ENGIN. 
LIBRARY 


A  PRELIMINARY  REPORT 

Prepared  for  Submission  to  its  Principals 

BY 

THE    AMERICAN  COMMITTEE 
ON  ELECTROLYSIS 

APPOINTED   BY 

National  Engineering  Societies 

and  other 
Interested  Associations  and  Corporations 


(PRINTED— NOT    PUBLISHED) 

This  preliminary  report  is  intended  to  include  only 
statements  of  fact.  It  does  not  .attempt  to  draw  conclusions 
or  to  make  recommendations  or  to  discuss  questions  of  law. 


NEW  YORK  CITY 
October,  1916 


TVf 


Engineering 
Library 


Additional  copies  of  this  report  may  be  procured 
from  the  Secretary  of  the  American  Institute  of 
Electrical  Engineers,  33  West  39th  St.,  New  York. 

at 
One  dollar  per  copy. 


COMMITTEE 

BION  J.  ARNOLD,  Chairman 

American  Electric  Railway  Association. 

ALBERT  S.  RICHEY  Worcester,  Mass. 

R.  P.  STEVENS,  Youngstown,  O. 

CALVERT  TOWNLEY,  New  York  City, 

American  Gas  Institute. 

ALBERT  F.  GANZ,  Hoboken,  N.  J. 

J.  A.  GOULD,  Boston,  Mass. 

JACOB  D.  VON  MAUR,  St.  Louis,  Mo. 

American    Institute  of    Electrical   Engineers. 
BION  J.  ARNOLD,  Chicago,  111. 

F.  N.  WATERMAN,  New  York  City 

PAUL  WINSOR,  Boston,  Mass. 

American    Railway  Engineering   Association. 

D.  J.  BRUMLEY,  Chicago,  111. 

E.  B.  KATTE,  New  York  City, 
W.  S.  MURRAY,  New  Haven,  Ct. 

American  Telephone  and  Telegraph   Company. 
A.  P.  BOERI,  New  York  City, 

F.  L.  RHODES,  New  York  City, 
H.  S.  WARREN,  New  York  City, 

American    Water    Works   Association. 

A.  D.  FLINN,  -New  York  City, 

D.  D.  JACKSON,  New  York  City. 

E.  E.  MINOR,  New  Haven,  Ct. 

National  Bureau  of  Standards. 
E.  B.  ROSA,  Sec'y.  Washington,  D.C. 

National  Electric  Light  Association. 
L.  L.  ELDEN,  Boston,  Mass. 

D.  W.  ROPER,  Treas.  Chicago,  111. 

PHILIP  TORCHIO,  New  York  City, 

Natural  Gas  Association. 

B.  C.  OLIPHANT,  Buffalo,  N.  Y. 
FORREST  M.  TOWL,                              New  York  City, 
S.  S.  WYER,                                          Columbus,  O. 


v~. 


41489 


SUB-COMMITTEES 


1:  PLAN  AND  SCOPE: 

CALVERT  TOWNLEY,  Chairman. 
ALBERT  F.  GANZ, 
E.  B.  KATTE, 

D.  W.  ROPER, 

E.  B.  ROSA, 
H.  S.  WARREN, 

F.  N.  WATERMAN, 
S.  S.  WYER. 


2:  PRINCIPLES      AND      DEFINI- 
TIONS: 

E.  B.  ROSA,  Chairman, 
A.  P.  BOERI, 
D.  J.  BRUMLEY, 
D.  D.  JACKSON, 
R.  P.  STEVENS. 


PHILIP  TORCHIO,  Chairman, 
J.  A.  GOULD, 
W.  S.  MURRAY, 
FORREST  M.  TOWL, 
CALVERT  TOWNLEY. 


3:  METHODS    OF    MAKING       4:  EUROPEAN  PRACTICE: 
ELECTROLYSIS  SURVEYS : 

J.  D.  VON  MAUR,  Chairman, 
L.  L.  ELDEN, 

E.  E.  MINOR, 
B.  C.  OLIPHANT, 

F.  L.  RHODES, 
PAUL  WINSOR. 

6:  AMERICAN  PRACTICE:  6: 

F.  N.  WATERMAN,  Chairman, 

ALBERT  F.  GANZ, 

E.  B.  KATTE, 

ALBERT  S.  RICKEY, 

D.  W.  ROPER, 

H.  S.  WARREN 

S.  S.  WYER. 


PUBLICATION: 

E.  B.  KATTE,  CHAIRMAN, 
A.  D.  FLINN, 
ALBERT  F.  GANZ, 
ALBERT  S.  RICKEY, 

E.  B.  ROSA. 
PHILIP  TORCHIO, 
H.  S.  WARREN, 

F.  N.  WATERMAN, 
S.  S.  WYER. 


PREFACE. 

Those  familiar  with  the  history  of  the  electric  railway  in- 
dustry in  the  United  States  in  the  early  90's  and  subsequently 
for  a  decade,  will  recall  the  great  rapidity  with  which  the  electric 
railway  was  developed  and  the  litigation  that  resulted  between 
the  gas  and  water  companies  and  the  electric  railway  com- 
panies over  the  introduction  into  the  field  of  the  electric  rail- 
way using  a  grounded  return  circuit.  The  utility  companies 
whose  properties  were  threatened  with  damage  from  elec- 
trolysis due  to  these  grounded  return  circuits  of  the  railway  com- 
panies, attempted  by  all  legitimate  means  to  prevent  the 
acceptance  of  the  grounded  return  circuit,  with  the  result 
that  in  one  or  two  cases, — for  instance,  in  the  city  of  Cincinnati, 
a  complete  metallic  overhead  return  circuit  was  adopted  and  is 
still  in  operation,  but  the  electric  railway  operated  with  a 
grounded  return  circuit  in  connection  with  the  overhead  trolley 
became  the  standard,  and  rapidly  spread  throughout  the  country, 
and  still  remains  the  standard  for  electric  traction  systems. 

At  first  when  the  electric  railway  systems  were  small,  and 
light  cars  were  used,  the  quantity  of  current  flowing  through 
the  rails  was  not  large,  and  the  possibility  of  damage  from 
electrolysis  was  comparatively  small,  but  as  the  systems  were  ex- 
tended and  the  weight  and  number  of  cars  greatly  increased, 
the  problem  became  much  more  serious,  and  began  to  demand 
special  attention.  It  is  only  within  the  past  four  or  five 
years  that  the  subject  has  been  sufficiently  well  understood 
by  engineers  generally  to  make  it  probable  that  their  opinions 
could  be  made  to  agree  upon  standard  methods  for  the  pre- 
vention or  adequate  mitigation  of  electrolysis. 

At  the  present  time,  due  to  the  fact  that  the  grounded  return 
circuit  system  has  been  so  long  established  and  so  extensively 
adopted,  with  the  result  that  millions  have  been  invested  in 
copper  for  supplemental  rail  return  circuits,  the  engineers  now 
endeavoring  to  seek  a  solution  of  the  question  find  themselves 
confronted  with  the  problem  not  only  how  best  to  design  and  in- 
stall a  new  system  to  prevent  damage  from  electrolysis,  but  also 

5 


6  PREFACE 

what  can  be  done  with  the  electric  railway  systems  as  they 
exist  in  cities  today. 

While  recourse  to  the  courts  has  always  been  open,  the  prov- 
ing in  court  of  the  precise  amount  of  damage  that  has  been 
occasioned  by  electrolysis,  as  distinct  from  other  causes,  and 
accurately  proportioning  such  damage  between  various  elec- 
trical companies,  has  made  the  fixing  of  responsibility  extremely 
difficult.  In  view  of  this  unsatisfactory  condition  it  was  thought 
best  by  the  National  Societies  representing  those  connected  with 
the  various  utilities  involved  to  take  up  the  subject  compre- 
hensively and  endeavor,  if  possible,  by  co-operation  among  them- 
selves and  with  other  interested  associations  and  corporations  to 
gather  and  classify  information,  and  if  then  found  feasible  to 
agree  upon  and  recommend  methods  which  without  being  finan- 
cially prohibitive  will  nevertheless  practically  eliminate  damage 
from  electrolysis. 

The  American  Institute  of  Electrical  Engineers  with  this 
object  in  view  invited  the  following  bodies  to  officially  appoint 
representatives  to  serve  upon  a  committee  for  which  the  name 
The  American  Committee  on  Electrolysis  was  finally  adopted : 

American  Electric  Railway  Association. 

American  Gas  Institute. 

American  Institute  of  Electrical  Engineers. 

American  Railway  Engineering  Association. 

American  Telephone  &  Telegraph  Company. 

American  Water  Works  Association. 

National  Bureau  of  Standards. 

National  Electric  Light  Association. 

Natural  Gas  Association. 

The  first  meeting  of  the  Committee  was  held  in  the  Directors' 
Room,  American  Institute  of  Electrical  Engineers,  33  West 
39th  Street,  New  York  City,  May  27th,  1913,  to  make  pre- 
liminary arrangements,  and  the  second  meeting  held  at  the 
same  place  on  February  25,  1914,  resulted  in  the  selection  of 
a  permanent  chairman  and  secretary,  and  the  appointment  of 
the  various  sub-committees. 

The  result  of  the  work  of  these  sub-committees  is  embodied 
in  the  various  sections  of  the  accompanying  report. 

Owing  to  the  complexity  of  the  subject  and  the  need  for 
thorough  discussion  in  the  several  technical  bodies,  and  for 
further  investigation  by  the  interests  involved  the  Committee 
has  thought  best  not  to  attempt  to  issue  a  final  report  at  the 


PREFACE  7 

present  time,  but  has  endeavored  to  present  the  subject  in  this 
preliminary  report  by  such  statements  of  fact  as  its  members  can, 
at  this  time,  unanimously  agree  upon,  with  the  expectation  that, 
after  the  consideration  of  these  statements  of  fact  by  the  bodies 
whom  the  members  of  this  committee  represent,  and  such  further 
investigation  as  may  be  necessary  by  the  Committee,  a  report 
will  ultimately  be  prepared,  embodying  principles,  rules  and 
recommendations  which  will  form  a  basis  for  solving  this  com- 
plicated problem. 

New  York  City, 

September  21st,  1916. 


PRELIMINARY  REPORT. 

THE   AMERICAN    COMMITTEE  ON    ELECTROLYSIS. 

GENERAL  INDEX.  PAGE 

PREFACE:  A  General  Statement  of  the  Scope  of  the  Work.  5 

I:  PRINCIPLES  AND  DEFINITIONS: 
A.  ELECTROLYSIS  IN  GENERAL: 

1.  Electrolysis 13 

2.  Electrolyte,  Electrode,  Anode,  Cathode 13 

3.  Amount  of  Chemical  Action  (Faraday's    Law) 13 

4.  Cause  of  Current  Flow 14 

5.  Electrolysis  by  Local  Action 14 

6.  Anodic  Corrosion ....'. 14 

7.  Secondary  Reactions 14 

8.  Cathodic  Corrosion 15 

B.  ELECTROLYSIS    OF    UNDERGROUND    STRUCTURES: 

9.  General 15 

10.  Self  Corrosion 15 

11.  Acceleration  of  Local  or  Self  Corrosion 16 

12.  Coefficient  of  Corrosion. 16 

13.  Anodic  and  Self  Corrosion 16 

14.  Passivity 16 

15.  Polarization  Voltage 16 

16.  Alternating  or  Frequently   Reversed   Direct  Current 17 

17.  Action  on  Underground  Metallic  Structures 17 

18.  Stray  Current 18 

19.  Electrolysis  Mitigation 18 

20.  Electrolysis  Surveys 18 

21.  Overall  Potential  Measurements 18 

22.  Potential  Gradients 19 

23.  Positive  and  Negative  Areas 19 

24.  Drainage  Systems 19 

25.  Uninsulated  Track  Feeder  System 20 

26.  Insulated  Track  Feeder  System 20 

II:  METHODS  OF  MAKING  ELECTROLYSIS  SURVEYS: 
A.   GENERAL: 

27.  General  Principles  of  Electrolysis  Surveys 21 

28.  Electric  Railways 22 

29.  Earthed  Piping  Systems 24 

30.  Underground  Cable  Systems 28 

31.  Bridges,  Buildings  and  Other  Earthed  Structures 30 

32.  Steam  Railway  Rails -. .  , 31 

33.  General  Survey  Practices 32 

34.  Application  of  Remedial   Measures — Resurveys 36 

9 


10  GENERAL  INDEX 

B.  APPARATUS:  PAGE 

35.  Portable  Measuring  Instruments 38 

36.  Recording  Instruments 39 

37.  Normal  Electrode 40 

38.  Earth  Ammeter. : 40 

39.  Testing  Electrodes 43 

C.  RECORDS  AND  REPORTS: 

40.  General 43 

41.  Electric  Railways 45 

42.  Piping  Systems 45 

43.  Cable  Systems 45 

44.  Bridges  and  Buildings 46 

45.  General  Conditions 46 

III:  AMERICAN  PRACTICE:— General 

A.  MEASURES    APPLIED     TO     RAILWAYS: 

46.  Insulation 47 

(a)  Complete  Insulation 48 

(b)  Substantial  Insulation 48 

(c)  Partial  Insulation 48 

47.  Reduction  of  Track  Voltage  Drop 49 

(a)  Bonding 49 

(b)  Cross-bonds . ' 50 

(c)  Conductivity  and  Composition  of  Rails 51 

(d)  Reinforcement  of  Rail  Conductivity 52 

(e)  Use  of  Additional  Power  Supply  Stations  and  Distribu- 
tion of  Load 53 

48.  Three  Wire  Systems 55 

49.  Reversed.  Polarity  of  Trolley  System 56 

50.  Booster  System 57 

51.  Interconnection  of  Railway  Return  Circuits 58 

52.  Use  of  Alternating  Currents 58 

53.  Insulated  Track  Feeder  System 59 

B.  MEASURES    APPLIED    TO    AFFECTED    STRUCTURES: 

54.  Insulating  Joints  in   Iron  Pipes  and  Cable  Sheaths 61 

55.  Insulating  Pipes,  Cables  and  Structural  Steel  from  Earth..  ..  65 

56.  Shielding  or  the  Use  of  an  Auxiliary  Anode 68 

57.  Drainage  of   Earthed    Metallic  Structures 69 

(a)  Lead  Sheathed  Telephone  and  Power  Cables 69 

(b)  Pipe  Systems 70 

(c)  Structural  Steel 71 

C.  PATENTED  PROTECTIVE  SYSTEMS: 

58.  Foreign  and  Domestic  Patents 71 

D.  ORDINANCES  AND  DECISIONS: 

59.  Ordinances 71 

60.  Decisions  by  Courts 72 


GENERAL  INDEX  11 

IV:  EUROPEAN  PRACTICE:  PAGE 

A.  GENERAL: 

61.  Personal  Investigation  Necessary 73 

62.  Countries  Visited 73 

B.  GERMANY: 

63.  Laws  and  Ordinances 74 

64.  Commission  Recommendations 75 

65.  Construction 75 

66.  Conditions 75 

C.  ITALY: 

67.  Laws  and  Ordinances 76 

68.  Construction 76 

69.  Conditions 76 

D.  FRANCE: 

70.  Laws  and  Ordinances 76 

71.  Construction , 77 

72.  Conditions 77 

E    ENGLAND: 

73.  Laws  and  Ordinances 77 

74.  Construction 78 

75.  Conditions 78 

F.  SUMMARY  AND  CONCLUSIONS: 

76.  Germany,  Italy,  France,  England 79 

77.  Application  to  American  Conditions 79 

G.  REGULATIONS  ADOPTED  AND  PROPOSED: 

78.  Germany — Earth  Current  Commissions'  Recommendations..  81 

79.  France-^Regulations  by  Minister  of  Public  Works 99 

80.  England — British  Board  of  Trade  Regulations 101 

81.  Spain — Electric  Legislation. 107 

H.  SUMMARY  OF  EUROPEAN  CONDITIONS: 

82.  Present  Electrolysis  Conditions 107 

83.  Protective  Measures  in  Vogue 109 

Feeders 109 

Voltage  and    Current  Conditions - 110 

Miscellaneous   Protective  Measures Ill 

84.  Economic  Aspects  of  Electrolysis  Problem 115 

85.  Regulations  and  Tests 115 

I.     GENERAL    REMARKS: 

86.  Germany 116 

87.  France..                                                                                              .  117 


12  GENERAL  INDEX 

J.  STATISTICAL— OPERATING— STRUCTURAL  AND  TECH- 
NICAL DATA:  PAGE 

88.  Table  1 — Magnitude    of    Electric    Railway    Undertakings, 

German  Empire  and  United  Kingdom 117 

89.  Table  2 — Tramways   Not  Operated  by  Electricity,    German 

Empire  and  United  Kingdom 118 

90.  Table  3 — Ownership  of  Electric  Railway  Undertakings,  Ger- 

man Empire  and  United  Kingdom 118 

91.  Table  4 — Statistics    of  Tramways  in  Large  Cities,    German 

Empire  and  United  Kingdom 119 

92.  Table  5 — Statistics   of    Tramways    in   Small  Cities,  German 

Empire  and  United  Kingdom 120 

93.  Table  6 — Rail   Bonding   Data,  United   Kingdom 121 

94.  Table  7— Use  of  Negative  Boosters,    United  Kingdom 122 

95.  Table  8 — Distribution      Systems    for     Tramway     Feeders, 

United   Kingdom 122 

K.  CURVES    AND    SKETCHES: 

Curve — Graphical   representation   of  Electric  Railways  Sta- 
tistics, United  Kingdom,  1878  to  1912.      (Fig.  9) 123 

Sketch— Track  Construction,  United  Kingdom.      (Fig.  10) ...  124 

"     — Track  Construction,  Germany.     (Fig.  11) 125 

"      —German  Tramway  Rails.     (Fig.  12) 126 

"     —British  Tramway  Rails    (Fig.  13) 127 

Curve — Rail  Weight  Data.     (Fig.  14) 128 

Sketch— Typical  Rail  Bonds,  United  Kingdom.      (Fig.  15) ..  129 

"     — Cross  Bonding  Details,  United  Kingdom    (Fig.    16)  130 

L.    MISCELLANEOUS    NOTES: 

96.  Electrolysis  Testing  Methods 131 

97.  Abstract  of  Laws  and  Regulations  or  Recognized  Standards  in 

European  Countries 131 

98.  Plan  of  German  Earth  Commission  Reports 133 

99.  General  Comments  on  Reports 134 

V:  BIBLIOGRAPHY:  135 
VI:  APPENDICES.    (Tables.) 

100.  Table    9.     Resistance  of  Standard  Cast  Iron   Pipe 139 

101.  Table  10      Resistance  of  Standard  Steel  or  Wrought  Iron  Pipe  146 

102.  Table  11.     Resistance  of  Lead  Cable    Sheaths 148 

103.  Typical  Report  Sheets 149 


I.  PRINCIPLES  AND  DEFINITIONS. 

A.     ELECTROLYSIS  IN  GENERAL. 

1.  Electrolysis  is  the  process  by  which  chemical  changes  are 
caused  by  an  electric  current,  independent  of  any  heating  effect. 

NOTE.  These  changes  usually  occur  in  a  water  solution 
of  an  acid,  alkali  or  salt.  By  the  passage  of  an  electric  current 
through  it,  water  (containing  a  trace  of  acid)  is  decom- 
posed into  hydrogen  and  oxygen,  copper  is  deposited  from 
a  solution  of  copper  sulphate,  silver  from  solutions  of  silver 
salts.  Electroplating,  electrotyping,  and  refining  of  metals 
by  electrodeposition  are  useful  applications  of  electrolysis 
in  the  arts.  Electrolysis  is  involved  in  the  charge  and 
discharge  of  storage  batteries,  and  in  the  operation  of 
primary  batteries. 

In  order  that  electrolysis,  may  occur,  the  following  condi- 
tions must  be  present : 

(a)  There  must  be  a  flow  of  electric  current  through  a 
conducting  liquid  from  one  terminal  to  another; 

(b)  The   conducting  liquid  must  be  a  chemical  com- 
pound or  solution  which  can  be  altered  by  the  action  of  the 
electric  current. 

2.  Electrolyte,  Electrode,  Anode,   Cathode.     The  electrolyte 
is  the   solution    (or  fused  salt)  through  which  the  electric  cur- 
rent   flows;  the    conducting    terminals    are  the  electrodes;  the 
terminal    by    which    the    current     enters    the  solution  is  the 
anode\  the  terminal  by  which  it  leaves  is  the  cathode. 

NOTE.  The  chemical  changes  caused  by  the  current  may 
affect  both  the  electrolyte  and  the  electrodes.  In  the  case  of  a 
solution  of  copper  sulphate  with  copper  plates  as  electrodes, 
copper  is  removed  from  the  anode  by  the  current  and 
carried  into  solution;  an  equal  amount  of  copper  is  de- 
posited upon  the  cathode.  In  general,  the  metal  travels 
with  the  current  toward  the  cathode. 

3.  Amount  of  Chemical  Action.  -(Faraday's  Law).   The  amount 
of  chemical  action  taking   place  at  the   anode  and  also  at  the 
cathode   (as    expressed    by  Faraday's  law)  is  proportional  to 
(1)  the  strength  of  current  flowing,    (2)   the  duration  of  the 

13 


14  PRINCIPLES   AND    DEFINITIONS 

current,  and   (3)  the  chemical  equivalent  weights  of  the  sub- 
stances. 

NOTE.  Otherwise  expressed,  the  quantity  of  metal  or  other 
substance  separated  is  proportional  to  the  total  quantity 
of  electricity  passing  and  the  electro-chemical  equivalent 
of  the  substance  or  substances  concerned.  The  electro- 
chemical equivalent  of  a  metal  is  proportional  to  its  atomic 
weight  divided  by  its  valence.  Faraday's  law  is  so  exactly 
realized  in  practice  under  favorable  conditions  that  it  is 
used  as  the  basis  for  the  definition  of  the  international 
ampere,  one  of  the  fundamental  electrical  units. 

4.  Cause  of  Current  Flow.     The  current  flowing  through  the 
electrolyte  may  be  due  (1)  to  an  external  electromotive  force 
or  (2)  to  the  difference  of  potential  due  to  the  use  of  electrodes 
of  different  materials  or  to  solutions  of  different  concentrations. 

NOTE.  The  first  case  is  illustrated  by  electrolysis  of  dilute 
sulphuric  acid  using  two  lead  plates  and  an  external  battery ; 
the  second  by  the  electrolysis  of  the  same  solution  using 
a  zinc  and  a  copper  .plate,  which  touch  each  other  inside  or 
outside  the  solution.  The  first  occurs  in  charging  a  storage 
battery ;  the  second  in  the  discharging  of  a  primary  battery 
or  a  storage  battery. 

5.  Electrolysis   by   Local   Action.      Instead   of  two  plates  of 
different  metals  the  same  result  may  follow  with  one  plate  if  it 
is  chemically  impure  or  otherwise  heterogeneous,  when  immersed 
in  dilute  acid. 

NOTE.  Such  a  plate  excites  local  currents  and  a  loss  of 
metal  occurs  at  all  the  anode  areas.  This  local  action  causes 
impure  zinc  to  dissolve  rapidly  in  a  solution  which  has  no 
action  on  pure  zinc. 

6.  Anodic  Corrosion  is  the  term  applied  to  the  loss  of  metal 
by  electrolysis  at  the  anode. 

NOTE  .  When  iron  is  anode  the  iron  is  carried  into  solution 
by  the  current,  the  first  product  being  a  salt  of  iron,  the 
nature  of  which  depends  upon  the  character  of  the  elec- 
trolyte. In  dilute  sulphuric  acid,  ferrous  sulphate  is 
formed,  in  hydrochloric  acid,  ferrous  chloride,  etc.  These 
first  products  of  the  electrolysis  are  frequently  modified 
by  secondary  reactions. 

7.  Secondary    Reactions    are    the    chemical    changes    which 
occur  at  or  near  the  electrodes,  by  which  the  primary  products 


PRINCIPLES   AND    DEFINITIONS  15 

of  electrolysis  are  converted  into  other  chemical  substances, 
and  are  sometimes  followed  by  other  reactions. 

NOTE  .  Ferrous  hydroxide  formed  by  the  union  of  iron  with 
hydroxyl  ions  set  free  at  the  anode,  is  subsequently  con- 
verted into  iron  oxide  due  to  the  reactions  with  oxygen 
dissolved  in  the  electrolyte.  When  lead  is  cathode  in  an 
alkali  soil  or  solution,  the  alkali  metal  (such  as  sodium 
or  potassium)  reacts  with  water  at  the  cathode  and  forms 
alkali  hydroxide,  setting  free  hydrogen.  This  hydroxide 
may  (especially  after  the  current  ceases)  react  with  the 
lead  chemically  and  form  lead  hydroxide,  which  in  turn 
may  combine  with  carbon  dioxide,  forming  lead  carbonate. 

8.  Cathodic  Corrosion  is  the  term  applied  to  the  corrosion 
due  to  the  secondary  reactions  of  the  cathodic  products  of 
electrolysis,  as  described  in  the  preceding  paragraph.  The 
metal  of  the  cathode  is  not  removed  directly  by  the  electric 
current  but  may  be  dissolved  by  a  secondary  action  of  alkali 
produced  by  the  current. 

NOTE  :  The  anodic  corrosion  is  more  common  and  more 
serious;  cathodic  corrosion,  however,  sometimes  occurs  on 
lead  and  other  metals  that  are  soluble  in  alkali.  Cathodic 
corrosion  never  occurs  in  the  case  of  iron. 


B.     ELECTROLYSIS  OF  UNDERGROUND  STRUCTURES. 

9.  General.     In  the  electrolysis  of  gas  and  water  pipes,  cable 
sheaths,  and  other  underground  metallic  structures,   and  the 
rails  of  electric  railways,  the  moisture  of  the  soil  with  its  dis- 
solved acids,  salts,  and  alkalis  is  the  electrolyte,  and  the  metal 
pipes,  cable  sheaths  and  rails  are  the  electrodes.  • 

NOTE.  Where  the  current  flows  away  from  the  pipes, 
the  latter  serve  as  anodes  and  the  metal  is  corroded. 
Metal  or  gas  or  alkali,  according  to  the  nature  of  the  soil, 
will  be  set  free  at  the  cathode. 

10.  Self  Corrosion  is  the  term  applied  when  a  "pipe  or  other 
mass  of  impure  or  heterogeneous  metal  buried  in  the  soil  is 
corroded  due  to  electrolysis  by  local  action. 

NOTE.  This  is  called  "self  corrosion"  because  the  elec- 
tric current  originates  on  the  metal  itself,  without  any 
external  agency  to  cause  the  current  to  flow.  Self  cor- 
rosion may  also  be  due  to  direct  chemical  action. 


16  PRINCIPLES   AND    DEFINITIONS 

11.  Acceleration  of  Local  or  Self  Corrosion.    Self  corrosion  is 
accelerated  by  the  presence  of  acids  or  salts  in  the  soil  water 
which  lower  its  resistance  as  an  electrolyte,  and  also  by  cinders, 
coke  or  other  conducting  particles  of  different  electric  potential 
which  augment  the  local  electric  currents.     In  the  latter  case  the 
metal  need  not  be  heterogeneous. 

NOTE.  A  pipe  may  be  destroyed  in  a  relatively  short 
time  by  self  corrosion  or  local  action  if  buried  in  wet 
cinders  or  in  certain  soils. 

12.  Coefficient  of  Corrosion.    The  coefficient  of  electrolytic  cor- 
rosion, (sometimes  called  corrosion  efficiency)  is  the  quotient  of 
the  total  loss  of  metal  due  to  anodic  corrosion  (after  deducting 
the  amount  of  self  corrosion  if  any)  divided  by  the  theoretical 
loss  of  metal,  as  calculated  by  Faraday's  law,  on  the  assumption 
that  the  corrosion  of  the  anode  is  the  only  reaction  involved. 

NOTE.  In  practice  it  is  found  that  the  coefficient  of 
corrosion  varies  widely  from  unity,  being  sometimes  as  low 
as  0.2  and  sometimes  even  above  1.5,  but  commonly  between 
0.5  and  1.1. 

13.  Anodic  and   Self   Corrosion.      Anodic   corrosion  due  to 
external  currents  and  self  corrosion   due  to  local  action  may 
occur  simultaneously,   and  the  former  may  accelerate  the  latter. 

NOTE.  Hence  the  corrosion  due  to  a  given  current  plus  the 
increased  self  corrosion  induced  by  that  current  may  give 
a  greater  total  corrosion  than  called  for  by  Faraday's  law. 
This  explains  how  the  coefficient  of  corrosion  may  exceed 
unity. 

14.  Passivity  is  the  name  given  to  the  phenomenon  in  which 
a  current  flows  through  an  electrolyte  without  producing  the 
full  amount  of  anodic  corrosion  which  would  occur  under  normal 
conditions. 

NOTE.  This  restricted  definition  of  passivity  has  regard 
only  to  its  effect  in  electrolysis.  Many  conditions  affect  the 
degree  of  passivity  attained,  an  initial  large  current  density 
being  favorable  to  it.  Plunging  iron  into  fuming, nitric 
acid  renders  it  temporarily  passive.  A  satisfactory  ex- 
planation of  passivity  has  not  been  given. 

15.  Polarization  Voltage   (sometimes  called  polarization  po- 
tential) is  the  temporary  change  in  the  difference  of  potential 


PRINCIPLES   AND    DEFINITIONS  17 

between  an  electrode  and  the  electrolyte  in  contact  with  it  due 
to  the  passage  of  a  current  to  or  from  the  electrode.  This 
change  in  potential  difference,  is  due  to  the  change  in  the  con- 
ditions of  the  surface  of  the  electrode  or  change  in  the  con- 
centration of  the  electrolyte  (or  both),  and  under  some  con- 
ditions is  approximately  proportional  to  the  current  flowing, 
but  in  many  cases  is  not  so  proportional.  'The  magnitude  of 
the  polarization  voltage  also  depends  on  the  material  of  the 
electrode,  the  nature  of  the  electrolyte  and  the  direction  of 
the  current. 

16.  Alternating  or    Frequently    Reversed    Direct    Currents. 

If  alternating  currents  (or  frequently  reversed  direct  cur- 
rents) flow  through  the  soil  between  pipes  or  other  under- 
ground metallic  structures,  the  metal  removed  during  the  half 
cycles  when  a  pipe  is  anode  may  be  in  part  replaced  when  it  is 
cathode.  Hence,  the  total  loss  of  metal  on  a  given  pipe  is  less 
than  one-half  of  what  it  would  be  if  the  pipe  were  an  anode 
with  direct  current  of  the  same  average  value  in  the  case  of 
frequently  reversed  direct  current  and  in  the  case  of  alternating 
current  at  commercial  frequency  it  is  less  than  1%  and  in  most 
cases  negligible.  (See  Section  52.) 

NOTE.  In  slow  reversals  of  current,  the  recovery  effect  is 
less, but  the  loss  will  be  less  than  with  direct  current  continu- 
ously in  the  same  direction  (excepting  possibly  where  the 
phenomenon  of  passivity  may  affect  the  result). 

17.  Action   on    Underground    Metallic    Structures.       Fara- 
day's   Law    applies    to    electrolysis   of   metallic  structures   in 
soil  as  elsewhere,  the  total  chemical  action  being  proportional 
to  the  average  current  strength  and  the  time  the  current  flows  and 
to  the  electrochemical  equivalent  of  the  metal  or  other  substances 
concerned.     Although  local  action  and  passivity  affect  the  loss 
of  metal  and  so  apparently  modify  Faraday's  law,  it  is  still  true 
that  the  total  chemical  action  resulting  from  the  current  flow 
is  proportional  to  the  total  current  when  local  currents  are  in- 
cluded. 

NOTE.  Sometimes  this  chemical  action  is  concerned  only 
with  corroding  the  anode;  sometimes  it  is  concerned  with 
breaking  up  the  electrolyte,  as  when  the  anode  is  a  noble 
metal  or  in  the  passive  state  (as  iron  and  lead  sometimes 
are) ;  sometimes  both  these  effects  occur. 

The   theoretical  loss   of  lead  from  a  lead  pipe  or  cable 


18  PRINCIPLES   AND    DEFINITIONS 

sheath  is  3.7  times  as  great  as  that  of  iron  (ferrous)  from 
an  iron  pipe  due  to  the  same  current  because  of  the  larger 
electrochemical  equivalent  of  lead. 

18.  Stray  Current.    If  the  railway  return  utilizes  the  grounded 
rails  of  the  tracks,  part  of  the  current  will  flow  off  the  rails  or 
other  grounded  returns  and  return  through  other  paths;  the 
current  observing  the  law  of  divided  circuits;  i.e.  the  current 
flows  through  all  possible  paths  in  parallel,  the  strength  of  cur- 
rent in  each  path  being  inversely  proportional  to  its  resistance. 
This  statement  excludes  the  effect  of  polarization  on  rails  and 
underground  structures,  which  in  some  cases  is  appreciable. 

19.  Electrolysis   Mitigation.     The   two   primary   features   of 
electrolysis  mitigation  are  (1)  the  reduction  of  the  flow  of  cur- 
rent through  the  earth  and  the  metallic  structures  buried  in  the 
earth,  (2)  the  reduction  of  the  anode  areas  of  such  structures 
to  a  minimum,  where  the  current  is  not  substantially  eliminated 
in  order  to  reduce  the  area  of  destructive  corrosion  as  far  as 
possible. 

NOTE:  The  current  in  the  underground  metallic  struc- 
tures will  be  decreased,  other  conditions  remaining  the 
same,  by  (1)  increasing  the  conductance  of  the  return  cir- 
cuit, (2)  increasing  the  resistance  of  the  leakage  path  to 
earth,  (3)  increasing  the  resistance  between  the  earth  and 
the  underground  metallic  structures,  (4)  increasing  the  re- 
sistance of  the  underground  metallic  structures. 

The  anode  areas  of  the  underground  metallic  structures 
will  be  decreased,  other  conditions  remaining  the  same,  by 
providing  suitably  placed  metallic  conductors  for  leading 
the  current  out  of  the  underground  structures  so  that  the 
flow  of  the  current  directly  to  the  earth  shall  be  minimized. 
This  will  change  a  portion  of  the  anode  area  to  cathode. 

20.  Electrolysis  Surveys.     A  term  applied  to  investigations 
made  to  determine  the  condition  of  grounded  metallic  structures 
and  the  soil  in  which  they  are  imbedded  and  of  the  overall  drops, 
potential  gradients,  local  potential  conditions,  current  densities, 
etc.  in  the  railway  tracks,  or  other  grounded  metallic  structures, 
and  positive  and  negative  feeders  connected  to  them  to  deter- 
mine what  conditions  tending  to  produce  damage  exist. 

21.  Overall   Potential     Measurements.      Overall     potential 
measurements  show  the  difference  in  electric  potentials  between 


PRINCIPLES   AND    DEFINITIONS  19 

points  in  the  tracks  at  the  feed  limits  of  the  station  and  the 
point  in  the  tracks  which  is  lowest  in  potential,  and  are  obtained 
by  means  of  pressure  wires  and  indicating  or  recording  volt- 
meters. 

NOTE:  The  pressure  wires  may  be  telephone  or  other 
wires  utilized  temporarily,  or  wires  permanently  installed 
for  the  purpose. 

22.  Potential  Gradients.    The  potential  gradient  is  the  rate 
of  change  of  electric  potential  along  the  rails  of  a  track  or  other 
grounded   structure  in   the   earth,  and  is  usually  expressed  in 
volts  per  thousand  feet  or  volts  per  kilometer. 

23.  Positive  and  Negative  Areas.    Positive  areas  are  those 
areas  where  the  current  is  in  general  leaving  the  pipes  or  other 
underground  metallic  structures  for  the  earth.     Such  areas  are 
often  called  danger  areas. 

Negative   areas  are  those  areas  where  the  current  is  in  gen- 
eral flowing  to  the  pipes  or  other  underground  metallic  structures. 

NOTE  :  As  the  current  often  flows  from  one  underground 
metallic  structure  to  another,  it  is  evident  that  within  a 
positive  area  there  are  local  negative  areas  and  vice  versa. 
Hence  the  terms  are  applied  somewhat  loosely,  and  according 
to  which  condition  predominates. 

Besides  the  positive  and  negative  areas  there  are  areas 
of  more  or  less  indefinite  extent  in  which  the  current  flow  be- 
tween metallic  underground  structures  and  earth  normally  re- 
verses between  positive  and  negative  values.  These  areas 
are  called  neutral  areas  or  neutral  zones. 

24.  Drainage   Systems.      A  drainage  system  is  one  in  which 
wires  or  cables   are  run    from  a  negative  return  circuit   of  an 
electric  railway  and  attached  to  the  underground  pipes,  cable 
sheaths  or  other  underground  metallic  structures  which  tend  to 
become  positive  to  earth,   so  as  to   conduct  current  from  such 
structures  to  the  power  station,  thereby  tending  to  reduce  the 
flow  of  current  from  such  structures  to  earth. 

NOTE.  Three  kinds  of  drainage  systems  may  be  dis- 
tinguished. (1)  where  direct  ties  with  wires  or  cables  are 
made  between  underground  metallic  structures  and  tracks, 
(2)  where  uninsulated  negative  feeders  are  run  from  the 
negative  bus  to  underground  metallic  structures,  (3)  where 
separate  insulated  negative  feeders  are  run  from  the 
negative  bus  to  underground  metallic  structures,  or  a  main 
feeder  with  taps  to  such  structures. 


20  PRINCIPLES   AND    DEFINITIONS 

25.  Uninsulated    Track    Feeder     System.     An  uninsulated 
track  feeder  system  is  one  in  which    the    return   feeders  are 
electrically  in  parallel  with  the  tracks.      Under  such  circum- 
stances   the    cables    may    be     operating     very  inefficiently  as 
current  conductors  and  as  a   means  of  reducing  track  voltage 
drop,  particularly  where  voltage  drops  in  the  earth  portion  of 
the  return  are  maintained  at  the  low  values  usually  required 
for  good  electrolysis  conditions.     (See  Section  47  (d)). 

26.  Insulated    Track    Feeder    System.     An   insulated  track 
feeder    system,    sometimes    called    an   insulated   return   feeder 
system,  is  one  in  which    insulated    wires    or    cables    are    run 
from  the  insulated  negative  bus  in  a  railway  power  station  and 
attached  at  such  places  to  the  rails  of  the  track  as  to  take  cur- 
rent from  the  track  and  conduct  it  to  the   station,   in  such  a 
manner  as  to  reduce  the  potential  gradients  in  the    tracks  and 
the    differences    of    potential    between    underground    metallic 
structures  and  rails,  and  so  reducing  the  flow  of  current  in  un- 
derground metallic  structures.     (See  section  53). 

NOTE.  The  insulated  negative  feeders  may  run  separately 
from  the  negative  bus  to  various  points  in  the  track  network, 
or  a  smaller  number  of  cables  may  be  used  with  suitable 
resistance  taps  made  to  tracks  at  various  places. 

With  this  system  the  drop  of  potential  in  the  track 
feeders  is  independent  of  the  drop  of  potential  in  the  tracks. 


ELECTROLYSIS   SURVEYS  21 


METHODS  OF  MAKING  ELECTROLYSIS 
SURVEYS. 

A:  GENERAL. 

27.  General  Principles  of  Electrolysis  Surveys.  The  princi- 
pal measurements  made  in  electrolysis  surveys  of  under- 
ground structures  are  measurements  of  the  potential  differ- 
ences between  the  structure  tested  and  all  other  neighboring 
metal  structures  in  earth,  neighboiing  rails,  and  neighboring 
earth,  and  measurements  of  current  flow  on  selected  sections  of 
the  structural  system  under  test.  The  potential  difference  be- 
tween the  structure  tested  and  earth  affords  more  complete 
information  than  can  be  secured  from  the  results  of  any 
other  practicable  class  of  observations.  The  difficulties  are, 
however,  to  make  these  measurements  so  as  to  obtain 
the  true  potential  difference  between  the  earth  and  the 
earthed  structure,  and  frequently  also  to  obtain  contact  with 
earth  in  the  immediate  neighborhood  of  the  structure  tested. 
If  an  electrode  is  used  for  the  earth  potential  measurement,  not 
consisting  of  the  same  metal  as  the  structure  tested  an 
error  may  still  be  introduced  due  to  difference  in  the  polariza- 
tion potential  of  the  two  electrodes.  A  non-polarizable  electrode 
has  been  devised  by  Dr.  Haber,  as  described  later  in  this  report, 
but  it  has  been  used  only  to  a  very  limited  extent  in  this  country. 
On  account  of  the  difficulties  of  making  earth  potential  measure- 
ments, measurements  of  the  potential  differences  between  the 
structure  that  is  being  surveyed  and  neighboring  metal  structures 
are  much  more  generally  made. 

Measurements  of  stray  current  flowing  in  selected  sections  of 
any  structural  system  are  practicable  if  a  suitable  length 
of  the  structure  can  be  made  accessible.  By  comparison  of  such 
measurements  conclusions  can  be  reached  as  to  the  areas  in 
which  stray  currents  are  being  taken  from  or  delivered  to  the 
earth  and  as  to  the  amounts  of  current  which  are  concerned  in 
these  exchanges.  Measurements  of  this  character  usually 
cannot  be  made  on  sections  so  close  together  as  to  give  for 


22  ELECTROLYSIS   SURVEYS 

many  points  definite  values  for  the  current  flowing  to  or  from 
earth  on  account  of  the  high  cost  of  the  necessary  excavations 
and  permanent  replacements.  We  have  therefore  included  a 
description  of  the  "  earth  ammeter  "  which  has  been  used 
abroad,  and  to  a  limited  extent  also  in  this  country,  for  ob- 
taining direct  measurements  of  current  flow  in  the  earth. 

A  survey  of  the  earthed  structures  which  are  liable  to  electrolytic 
corrosion  by  stray  currents  consists  in  making  such  observations 
relating  to  their  electrical  condition  as  may  determine  the  route 
followed  by  the  stray  cunent  and  its  degree  of  concentration, 
thereby  permitting  deductions  to  be  made  relative  to  the 
extent  and  the  intensity  of  the  electrolytic  injury  to  which 
the  structures  may  be  subjected.  While  measurements  of 
potential  are  most  frequently  made  (to  such  an  extent  that 
the  term  ;<  Potential  Survey  "  is  often  applied  to  this 
work),  it  should  be  borne  in  mind  that  the  real  object 
of  the  survey  is  to  determine  where  current  may  flow  from 
structure  to  earth  or  from  earth  to  structure  and  the  magnitude 
of  the  current  flowing  for  each  of  the  smallest  sections  into 
which  the  structure  can  practically  be  subdivided. 

In  discussing  methods  of  survey,  the  measurements  of  poten- 
tial and  current  peculiar  to  each  class  of  earthed  structures  will 
first  be  described,  together  with  any  special  observations  or 
precautions  to  be  taken.  A  discussion  of  the  measurements  of  a 
general  nature  common  to  all  classes  of  structures  will  then 
follow.  Measuring  instruments  and  other  apparatus  employed 
in  connection  with  this  work  will  be  described  in  detail  in  the 
section  devoted  to  apparatus. 

28.  Electric  Railways.  Before  making  measurements  re- 
lating to  an  electric  railway  system  the  available  informa- 
tion as  to  its  extent,  its  construction  features  and  particularly 
the  arrangement  of  its  earthed  return  circuit  and  the  connections 
thereto  should  be  collected.  The  best  available  maps  should 
be  procured  and  all  information  pertinent  to  the  electrolysis 
investigation  recorded,  either  by  annotation  on  a  suitably 
arranged  map,  or  in  some  other  convenient  form.  All  electrical 
connections  made  for  any  purpose  with  the  rails  or  other  parts 
of  the  return  circuit  should  be  noted  with  special  care,  and  the 
location  of  any  structures  to  which  connection  is  thus  made 
ascertained  and  recorded. 

The  principal  measurements  to  be  made  upon  the  grounded 
return  system  of  an  electric  railway  are  as  follows : 


ELECTROLYSIS   SURVEYS  23 

1.  Potential    differences    between    the    point    of   lowest 
potential  on  the  tracks,  and  selected  points  on  the  tracks 
throughout  the  feeding  district  of  the  station  under  observa- 
tion. 

2.  Potential  gradient  measurements  along  the  railway 
tracks  to  determine  the  difference  of  potential  between 
points  on  the  track  separated    from    each    other    by   dis- 
tances of  from  1,000  to  3,000  feet. 

3.  Differences    of    potential    between    all    points    where 
negative   feeders   or   other   connections   between   bus-bars 
and  rail  return  make  contact  with  track;  also  differences  of 
potential  between  these  points  and  the  station  bus-bar. 

4.  Currents  carried  by  each  separate  connection  between 
bus-bar  and  rail. 

For  most  of  the  potential  measurements  listed  above, 
it  is  necessary  to  have  available  insulated  wires  con- 
nected with  all  points  on  the  railway  return  system,  whose 
potential  relations  are  to  be  determined,  all  of  these 
insulated  wires  being  brought  to  some  common  point  so 
that  measurements  may  be  made  between  them.  Where  pilot 
wires  have  been  installed  by  the  electric  railway,  many,  if  not 
all  of  the  points  at  which  it  is  desired  to  make  tests  will  be 
accessible  without  the  necessity  of  any  special  preparations. 
Where  pilot  wires  are  not  available  or  where  it  is  desired  to 
reach  points  not  included  in  the  pilot  wire  system,  the  most 
economical  plan  will  be  to  procure  the  use  of  any  avail- 
able circuits  found  in  the  local  telephone  distribution 
system.  Short  lengths  of  insulated  wire  will  need  to  be 
run  to  connect  such  circuits  with  the  tracks  and  the  testing 
circuits  thus  established  can  readily  be  brought  together  at  some 
common  point  for  measurements  between  them.  Where  neither  of 
the  above  alternatives  is  available,  wires  can  be  installed  in  some 
temporary  manner  over  available  pole  line  routes  to  connect 
with  the  points  whose  potentials  are  to  be  observed.  Such 
wires  should  be  insulated  from  earth  except  at  the  point  where 
they  connect  with  the  tracks. 

When  the  testing  circuits  are  established,  the  required  poten- 
tial measurements  should  be  obtained  by  connecting  to  a  volt- 
meter the  wires  leading  to  the  two  points  where  difference  of 
potential  is  to  be  determined.  The  voltmeter  should  be  kept 
in  circuit  and  under  observation  for  a  time  sufficient  to  insure 
that  the  normal  fluctuations  of  the  railway  load  have  been 
accounted  for.  When  long  time  observations  of  the  potential 
difference  between  two  points  are  desired,  a  recording  voltmeter 


24  ELECTROLYSIS   SURVEYS 

should  be  employed.  If  circuits  to  a  sufficient  number  of  points 
have  been  installed,  the  measurements  of  potential  gradient  in  the 
tracks  may  be  taken  by  connecting  the  proper  wires  at  the  central 
point  to  the  voltmeter.  If  the  requisite  number  of  pressure 
wires  for  gradient  tests  is  not  available,  these  measurements  may 
be  obtained  by  carrying  a  suitable  length  of  insulated  wire  along 
the  track  and  connecting  it  through  a  voltmeter  to  the  track  at 
the  two  points  between  which  the  gradient  is  to  be  measured. 

Measurements  of  current  flowing  in  negative  feeders  or  in 
other  connections  to  the  track  return  can  be  taken  by  inserting 
an  ammeter  in  the  circuit  to  be  measured,  when  this  is  possible, 
or  by  taking  the  voltage  drop  along  some  accessible  section  of 
the  connecting  lead,  which  is  sufficiently  uniform  in  dimensions 
to  permit  of  a  ready  calculation  of  its  resistance.  It  is  important 
that  all  such  measurements  of  current  should  be  taken  either 
simultaneously  with  measurements  of  potential  difference  be- 
tween the  bus-bar  and  the  track  end  of  the  connection,  or 
under  such  conditions  as  to  permit  of  their  accurate  correlation 
with  the  potential  observations.  A  station  load  curve  should 
also  be  obtained  on  account  of  the  information  which  it  gives 
as  to  the  characteristics  of  the  power  supply. 

Measurements  of  rail  bond  resistance  are  not  necessarily  a 
part  of  the  work  to  be  done  in  an  electrolysis  survey.  It  is, 
however,  occasionally  necessary  in  connection  with  a  survey  to 
test  the  resistance  of  particular  rail  bonds  in  order  to  obtain 
data  necessary  for  the  explanation  of  results  obtained  in  making 
some  of  the  regular  measurements.  When  such  tests  are  made, 
the  fall  of  potential  across  the  joint  in  the  rail  should  be  observed 
simultaneously  in  comparison  with  the  difference  of  potential 
for  some  short  measured  length  of  the  adjacent  rail.  If  one  of 
the  special  rail  bond  testing  devices  is  not  available  for  this  work, 
two  voltmeters  can  be  employed  and  read  simultaneously,  or  one 
voltmeter  can  be  connected  with  a  quick  acting  switch  and 
employed  so  as  to  secure  practically  simultaneous  observations. 
This  latter  method  may  give  unreliable  results  unless  a  large 
number  of  readings  are  averaged. 

29.  Earthed  Piping  Systems.  Before  tests  are  made  to 
determine  the  electrolytic  condition  of  any  piping  system, 
all  available  information  as  to  its  extent  and  the  character- 
istics of  its  construction  should  be  collected  and  studied.  The 
best  available  maps  of  the  system  should  be  procured  and  any 


ELECTROLYSIS   SURVEYS  25 

special  information  of  importance  in  connection  with  an  elec- 
trolysis survey  not  noted  on  the  maps,  such  as  the  metals  of 
which  the  pipes  are  composed,  the  location  of  insulating  joints, 
the  relative  locations  of  other  piping,  and  cable  systems, 
the  location  of  electric  railway  tracks  and  return  circuits,  etc., 
should  either  be  recorded  upon  them  or  arranged  in  some 
convenient  form  for  reference. 

The  observations  which  should  systematically  be  taken  in 
examining  a  piping  system  are  as  follows: 

1.  Difference  of  potential  between  piping  system  and 
electric  railway  rails,  other  piping  systems,  cable  systems, 
metal  bridges,  steam  railway  rails,   etc.,   at  points  where 
these  cross  the  piping  system  or  come  in  close  proximity 
to  it.     (Potential  survey). 

2.  Measurements    of    potential    difference    between    ad- 
jacent hydrants,  or  adjacent  drip  or  service  connections. 
(This  will  serve  to  give  the  direction  of  the  current  flow- 
ing   in  the  pipe  line  and  some  rough  indications  of  its 
amount) . 

3.  Measurements  of  current  flowing  upon  exposed  sec- 
tions of  pipe.     (Current  survey). 

4.  Difference  of  potential  between  points  on  the  piping 
system  and  the  adjacent  earth  if  contacts  with  earth  can 
be  obtained. 

To  make  a  potential  survey,  potential  differences  between 
the  underground  pipes  and  rails  are  usually  measured  at  a 
number  of  points  along  every  street  where  there  are  pipes  and 
electric  railway  tracks.  Where  there  are  other  underground 
pipes  and  lead-sheathed  cable  systems,  it  is  desirable  to  make 
simultaneous  measurements  of  potential  difference  between 
the  piping  system  being  surveyed  and  the  neighboring  pipe 
and  cable  sheaths.  It  is  desirable  to  make  all  of  the  measure- 
ments of  potential  difference  at  any  one  point  simultaneously 
between  all  structures  tested.  Contact  with  the  underground 
pipes  for  these  potential  measurements  may  be  made  by  means 
of  service  pipes,  hydrants,  or  drip  connections.  The  connec- 
tions used  for  the  potential  measurements  may  be  tested  for 
electrical  continuity  by  means  of  an  ammeter  connected  be- 
tween the  contacts  with  a  dry  cell  in  series  if  necessary. 

Measurements  of  potential  difference  between  adjacent  test 
points  on  the  piping  system  should  also  occasionally  be  taken. 
As  the  resistance  of  pipe  joints  is  usually  not  uniform,  only 
an  approximate  idea  of  the  current  flowing  can  be  obtained 


26  ELECTROLYSIS   SURVEYS 

in  this  manner.  The  principal  object  of  this  test  is  to  obtain 
an  indication  of  the  direction  of  the  flow  of  current. 

It  is  therefore  desirable  to  make  a  rather  large  number  of 
these  tests  at  quite  frequent  intervals,  since  the  results  may 
be  interpreted  only  in  a  general  way;  individual  tests  may 
be  expected  to  vary  widely,  and  in  some  cases  they  may  even 
conflict.  This  test  may  be  made  for  shorter  intervals  and  in 
greater  detail,  where  some  sudden  change  of  potential  difference 
to  earth  or  neighboring  structures  has  been  observed.  Owing  to 
the  uncertainties  as  to  resistance  of  joints  it  is  best  not  to  at- 
tempt to  translate  these  voltage  readings  into  terms  of  current. 
They  may,  however,  be  used  in  comparisons  to  assist  in  fixing 
the  points  for  more  accurate  measurements  of  current  as 
described  in  the  next  paragraph. 

When  the  potential  observations  have  been  completed  and 
transferred  to  a  map  or  in  some  other  way  assembled  for  study, 
consideration  should  be  given  to  them  with  a  view  to  deter- 
mining what  parts  of  the  piping  system  appear  likely  to'be  re- 
ceiving substantial  amounts  of  current  from  earth  or  passing 
substantial  amounts  of  current  to  earth.  The  neutral  sections 
of  piping  between  positive  and  negative  potential  zones 
should  also  be  located.  With  this  information  at  hand  sections 
of  the  piping  system  should  be  selected  both  in  the  positive 
and  negative  zones  and  in  the  neutral  area  at  which  excavations 
can  be  made  and  determinations  of  the  current  flowing  in  the 
pipes  obtained.  In  selecting  points  for  excavations,  preference 
should  in  general  be  given  to  the  main  piping  routes,  but 
attention  should  also  be  given  to  any  branch  lines  which  appear 
likely  to  be  receiving  or  delivering  relatively  large  amounts  of 
current.  Any  cases  where  sections  of  the  system  located  with- 
in the  " negative  area"  give  positive  readings  to  earth,  should 
also  be  given  preference  in  this  study. 

The  method  of  measuring  current  consists  in  determining  the  fall 
of  potential  along  a  measured  length  of  pipe  of  known  di- 
mensions. For  the  purpose  of  this  measurement  it  will  generally 
be  found  advisable  to  attach  insulated  wires  permanently  to 
the  pipe  and  to  carry  them  to  some  suitable  point  underneath 
the  sidewalk  from  which  they  may  be  led  up  to  the  surface  to 
terminate  in  service  or  other  suitable  boxes  so  as  to  be  available 
for  measurements  of  current  in  the  future  after  the  excavation 
has  been  filled.  (See  Fig.  1.)  Tables  giving  the  resistances  of  unit 
lengths  of  pipe  of  different  diameters  and  materials  are  attached 


ELECTROLYSIS   SURVEYS 


27 


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1  O 

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cr 

D 
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a 

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28  ELECTROLYSIS   SURVEYS 

to  this  report.  (See  Appendix  Tables  9- 10).  The  current  flowing  in 
the  pipe  may  be  obtained  by  computation  from  the  observed 
drop  of  potential  and  the  unit  resistance  for  the  class  and 
weight  of  pipe. 

In  addition  to  the  observations  made  upon  the  piping  system, 
careful  attention  should  be  given  to  the  condition  of  the 
service  pipes  to  buildings,  particularly  in  locations  where  the 
services  cross  other  piping  systems,  cable  systems,  etc.  The 
potential  between  these  service  pipes  and  earth  and  between 
the  service  pipes  and  the  other  earthed  structure  crossed  should 
be  determined.  It  will  not  be  within  the  scope  of  the  usual 
survey  to  determine  the  condition  of  all  service  pipes  in  the 
area  covered,  but  it  is  desirable  that  some  of  the  services 
be  tested  in  order  to  ascertain  whether  there  is  any  serious 
tendency  towards  the  local  electrolytic  corrosion  of  service 
pipes.  When  buildings  are  entered  for  the  purpose  of  testing 
service  connections,  tests  of  potential  should  always  be  made 
to  any  other  service  pipes  or  cables  which  enter  the  same  build- 
ing, in  order  to  detect  cases  where  one  structural  system  is 
making  contact  with  the  other.  Current  measurements  may 
also  conveniently  be  made  on  service  pipes  in  buildings,  since 
the  pipes  are  exposed.  Such  tests  should  be  made  frequently, 
as  they  often  reveal  an  interchange  of  stray  current  between 
piping  systems  which  may  be  in  contact  in  the  building. 

30.  Underground  Cable  Systems.  Before  tests  are  made 
to  determine  the  electrolytic  condition  of  any  cable  system, 
all  available  information  as  to  its  extent  and  the  charac- 
teristics of  its  construction  should  be  studied.  Available 
maps  of  the  system  should  be  procured  and  any  special  in- 
formation of  importance  in  connection  with  an  electrolysis 
survey  not  noted  on  the  maps,  such  as  the  metals  used  for  the 
armor  or  sheathing  of  cables,  the  location  of  drainage  connec- 
tions, insulating  joints  and  other  protective  devices,  the  relative 
locations  of  other  cable  systems  and  of  piping  systems,  the 
location  of  the  electric  railway  tracks  and  return  circuits,  etc., 
should  either  be  recorded  by  annotation  upon  them  or 
arranged  in  some  convenient  form  for  reference. 

The  observations  which  should  systematically  be  taken  in 
examining  the  cable  system  are  as  follows: 

1.  Difference  of  potential  between  the  cable  system  and 
electric  railway  rails,  other  cable  systems,  piping  systems, 


ELECTROLYSIS   SURVEYS  29 

metal  bridges,  steam  railway  rails,  etc.,  at  points  where 
these  cross  the  cable  system  or  come  in  close  proximity 
to  it. 

2.  Difference  of  potential  between  points  on  the  cable 
system  and  the  adjacent  earth. 

3.  Difference   of   potential   between   cables   in   the  same 
subway  system  where  they  are  not  cross  bonded. 

4.  Current  flowing  upon  the  cables. 

In  making  surveys  the  potential  of  the -cable  with  respect  to 
the  adjacent  earth  should  always  be  determined  at  each  test- 
ing point.  In  original  surveys  the  greatest  practicable  number 
of  testing  points  should  be  utilized.  In  some  systems  it  will 
be  desirable  to  test  at  every  manhole,  but  in  extensive  networks 
of  power  cables  it  will  ordinarily  be  sufficient  to  test  at  less 
frequent  intervals  in  many  districts,  if  tests  are  made  at  shorter 
intervals  in  the  most  important  places.  The  potential  difference 
between  the  cable  and  rails  in  the  same  street  should  also  be 
determined,  but  in  cases  where  the  street  railway  rails  parallel 
the  cable  route  for  a  considerable  distance,  such  tests  may  be 
made  less  frequently.  If  pipes  or  other  earthed  metallic  struc- 
tures run  close  to  the  cable  system  at  the  point  of  testing,  it  is 
desirable  that  the  potential  difference  between  the  cable  system 
and  the  other  structure  be  determined,  provided  an  electrical 
connection  can  be  made,  e.g.,  through  a  hydrant,  etc. 

Tests  to  determine  the  direction  and  amount  of  stray  current 
flowing  on  the  cable  sheaths  should  be  made  at  appropriate 
intervals.  In  fairly  simple  cable  systems,  with  few  laterals, 
it  may  be  sufficient  to  make  these  tests  at  comparatively  infre- 
quent intervals,  such  as  every  fifth  manhole.  In  complicated 
networks,  however,  such  as  power  distribution  systems  with 
many  branches  and  service  connections,  it  will  generally  be 
desirable  to  test  more  frequently.  The  current  flowing  on  the 
cable  sheath  is  to  be  calculated  from  the  observed  fall  of  potential 
over  a  measured  length  of  sheath,  and  the  known  resistance  of 
this  length  of  sheath.  A  table  for  determining  current  on  lead 
cable  sheaths  from  voltage  drop  in  measured  length  of  sheath  is 
appended.  (See  Table  11.) 

In  the  course  of  the  survey,  measurements  should  also  be 
made  of  the  current  flowing  in  any  drainage  connections  or  in 
any  accidental  connections  which  connect  the  cable  system  with 
the  electric  railway  return  if  any  such  exist.  In  case  insulating 
joints  have  been  inserted  to  protect  any  parts  of  the  cable 
system  from  electrolytic  corrosion,  measurements  of  the  po- 


30  ELECTROLYSIS   SURVEYS 

tential  difference  between  cable  sheath  and  earth  should  be 
made  at  each  side  of  the  insulating  joint,  and  also  of  the  dif- 
ference in  potential  across  the  joint. 

In  a'  preliminary  study  it  should  be  ascertained  whether 
it  is  the  local  practice  to  insulate  from  the  main  cable  system 
those  branches  which  enter  buildings.  When  such  branches  are 
not  insulated  from  the  main  system,  tests  of  difference  of  potential 
should  be  made,  between  the  branch  cable  and  any  pipes  or  other 
cables  which  may  enter  the  same  building.  From  such  tests 
it  may  be  ascertained  whether  there  are  accidental  contacts 
between  the  cable  system  and  other  earthed  structures  within 
buildings,  and  if  any  such  are  found  in  a  portion  of  the 
total  number  of  installations,  a  conclusion  can  then  be 
reached  as  to  the  desirability  of  checking  the  conditions 
in  all  buidlings  entered.  In  localities  where  it  is  the  practice 
to  insulate  from  the  main  system  cable  branches  entering 
buildings,  the  possibility  of  defective  insulation  should  be 
checked  by  measuring  the  potential  difference  between-  cable 
inside  of  the  building  and  cable  outside  at  some  point  beyond 
the  supposed  location  of  any  insulating  joint.  Tests  for  differ- 
ences of  potential  between  the  branch  cable  and  other  metal 
structures  within  a  building  can  be  omitted  in  case  the  insulating 
joint  is  found  to  be  in  good  condition. 

The  condition  of  the  bonds  installed  to  equalize  the  potential 
of  the  cables  entering  such  manhole  should  be  observed  and 
noted.  If  bonds  are  lacking,  or  if  it  is  suspected  that  the  con- 
dition of  any  bond  is  faulty,  observations  of  the  difference  of 
potential  between  the  cables  should  be  taken  and  recorded. 

31.  Bridges,     Buildings    and     Other    Earthed     Structures. 

Through  the  study  of  maps,  etc.,  collected  as  preparatory 
data  for  surveys  of  piping  and  cable  systems,  informa- 
tion will  presumably  have  been  secured  concerning  the  locations, 
and  some,  at  least,  of  the  structural  characteristics,  of  the 
highway  and  railway  bridges  located  within  the  area  to  be 
studied.  The  locations  of  steam  railway  tracks  will  similarly 
have  been  obtained. 

In  making  electrolysis  surveys  of  bridges,  measurements  of 
potential  to  earth  should  be  made  at  each  end  of  the  metal 
structure.  In  case  the  bridges  are  crossed  by  electric  railway 
tracks,  piping  systems  or  cable  systems,  measurements  should 
also  be  made  from  the  metalwork  of  the  bridge  to  these  struc- 


ELECTROLYSIS   SURVEYS  31 

tures  to  determine  whether  there  is  any  difference  in  potential 
between  them.  Where  the  metalwork  of  the  bridge  structure, 
piers,  or  other  intermediate  supports  makes  contact  with  earth 
or  with  water,  measurements  of  potential  difference  to  earth 
or  to  water  also  should  be  made.  The  observer  should  follow 
up  closely  any  indication  of  poor  electrical  contact  between 
different  sections  of  the  metalwork  of  the  bridge,  or  between 
the  metalwork  and  any  other  of  the  earthed  structures  crossing 
the  bridge  which  are  supposed  to  be  in  good  electrical  contact 
with  the  metalwork. 

In  the  course  of  the  survey,  metal  frame  buildings  may  be  found 
in  locations  where  it  would  be  possible  for  them  to  collect  appreci- 
able amounts  of  current,  either  directly  through  the  earth  or 
indirectly  through  the  contact  of  rails,  pipes,  or  cables  with 
the  framework.  If  it  appears  that  such  contacts  exist,  measure- 
ments by  the  fall  of  potential  method  should  be  made  to  ascer- 
tain whether  appreciable  currents  are  flowing  into  the  building 
through  these  contacts,  if  this  is  found  to  be  the  case  tests  should 
be  made  at  a  number  of  points  from  the  building  structure  to 
ground  for  the  purpose  of  determining  where  the  current  leaves 
the  framework  and  whether  there  is  any  indication  that  ap- 
preciable damage  is  being  done.  In  the  case  of  buildings 
extending  over  a  considerable  area  it  is  desirable  that  measure- 
ments of  potentials  be  made  from  the  framework  to  earth*  at 
a  number  of  points,  even  in  case  no  contacts  are  found  between 
the  metal  framework  of  the  building  and.  other  metal  structures 
which  may  be  carrying  stray  currents. 

32.  Steam  Railway  Rails.  Steam  railway  rails,  either  through 
direct  contact  with  electric  railway  rails  or,  in  the  absence  of  an 
insulating  ballast,  through  contact  with  earth,  are  liable  at 
times  to  collect  and  discharge  appreciable  amounts  of  stray 
current,  and  this  may  occur  in  such  a  manner  as  to  be  detri- 
mental to  the  track  rails,  spikes  and  adjacent  earthed  structures. 
Because  of  this,  as  has  already  been  indicated,  measurements  of 
potential  to  steam  railway  rails  should  be  made  whenever  the 
structures  that  are  being  surveyed  are  in  close  proximity  to  steam 
railway  tracks,  and  it  is  also  desirable  to  determine  directly  by 
survey  the  condition  of  metal  steam  railway  bridges  as  well  as 
the  condition  of  metal  highway  bridges.  When  steam  railways 
are  equipped  for  electric  block  signaling  the  signal  battery  will 
affect  the  potential  of  the  rails.  The  potential  due  to  the  signal- 


32  ELECTROLYSIS   SURVEYS 

ing  connection  is,  however,  practically  uniform  in  value  and  can 
be  determined  through  observations  made  at  times  when  no 
stray  current  can  be  flowing.  With  this  potential  fixed,  a  con- 
clusion as  to  the  presence  and  amount  of  any  potential  can 
readily  be  reached. 

33.  General  Survey  Practices.  All  measurements,  excepting 
24-hour  records,  should  be  made  during  the  period  of  normal 
load  on  the  portions  of  the  railway  system  which  are  suspected 
of  being  the  sources  of  stray  currents.  In  general,  it  is  desirable 
to  express  the  results  of  short  time  measurements  in  terms  of 
''average  day  load"  on  the  railway  system.  In  localities  distant 
from  the  source  of  railway  power  supply,  the  foregoing  consid- 
erations make  it  necessary  to  take  into  account  the  presence 
or  absence  of  moving  cars  at  points  beyond  the  testing  station, 
especially  on  the  tracks  nearest  to  the  structure  which  is  being 
tested.  In  such  localities  the  duration  of  a  test  should  be  ex- 
tended to  include  at  least  one  complete  cycle  of  car  movement, 
unless  previous  experience  at  other  testing  points  in  the  immediate 
neighborhood  have  clearly  indicated  that  parts  of  the  cycle 
may  safely  be  neglected.  As  the  railway  lines  converge  toward 
a  common  center,  or  as  the  source  of  railway  power  supply 
is  approached,  the  probability  of  normal  load  condition  increases 
but  even  under  these  conditions  it  is  necessary  for  the  tester  to 
insure  that  the  railway  load  conditions  are  substantially  normal, 
when  measurements  are  being  made. 

At  a  number  of  points  observations  of  potential  differences 
and  of  current  flowing  along  the  structure  should  also  be  made 
with  24-hour  recording  instruments  and  the  characteristics,  of 
these  currents  and  potentials  compared  with  the  characteristics 
of  railway  load  curves.  This  will  serve  to  indicate  whether 
the  current  and  the  potential  are  identified  with  the  railway 
source.  The  24-hour  averages  for  currents  and  potentials 
obtained  at  these  points  of  measurement  will  also  be  of  use  in 
indicating  what  allowances  should  be  made  in  the  readings 
taken  systematically  at  all  points  of  the  system  in  order  to 
make  them  represent  the  average  day  conditions. 

During  observations  of  potential  or  current  the  movements 
of  the  needle  in  the  measuring  instrument  should  be  closely 
watched  so  that  the  maximum  and  minimum  readings  may  both 
be  obtained  as  well  as  any  change  in  the  polarity  of  the  potential 
or  in  the  direction  of  the  current.  The  observer  should  also  bear 


ELECTROLYSIS   SURVEYS  33 

in  mind  that  collected  results  of  the  individual  tests  will  be 
plotted  on  a  map  or  otherwise  compared  so  as  to  get  a 
general  idea  of  the  conditions  prevailing.  When,  therefore, 
there  is  reason  to  believe  that  the  recorded  maxima  and  minima 
are  abnormal,  notes  should  be  made  giving  the  reasons  for  such 
a  belief  and  indicating  the  value  which  is  thought  to  be 
more  nearly  comparable  with  the  values  obtained  at  other 
points. 

In  regular  field  survey  work  portable  measuring  instruments, 
will  be  found  most  suitable  for  the  great  majority  of  the  measure- 
ments to  be  taken.  Occasionally,  however,  conditions  will 
arise  under  which  it  is  desired  to  observe  the  potential  or  the 
current  at  some  particular  point  for  several  hours  and  even 
for  one  or  more  24-hour  cycles.  In  the  case  of  such  long  period 
observations  recording  voltmeters,  milli voltmeters  and  am- 
meters will  be  found  of  great  assistance  and  should  be  employed 
if  available.  Instruments  of  this  kind  are  described  in  the 
apparatus  section.  (Sec.  35-39.) 

When  bodies  of  water  or  areas  of  swampy  earth  cross  or  are 
located  in  close  proximity  to  earthed  structures,  stray  current 
may  flow  from  the  structure  to  earth  locally.  This  is  par- 
ticularly true  if  the  water  is  brackish  or  salty.  In  case  such 
relatively  high  conductive  sections  of  the  earth  afford  a  path 
of  lower  resistance  for  the  return  of  current  than  the  structure 
itself,  the  probability  of  a  large  flow  of  current  to  earth  is 
considerable.  The  flow  of  current  from  the  earthed  struc- 
ture is  not  necessarily  stopped  when  such  highly  conductive 
strata  have  been  hidden  by  building  over  them  or  by 
filling  in  with  surface  soil.  It  is,  in  consequence,  neces- 
sary to  observe  closely  the  physical  geography  of  the 
areas  covered  by  the  survey  and  unless  the  observer  is  per- 
sonally familiar  with  the  history  of  the  locality  and  the 
changes  which  have  occurred,  it  is  desirable  for  him  to 
ascertain  the  facts  from  those  familiar  with  them.  If  the 
structure  under  observation  is  accessible  for  tests  at  intervals 
of  a  few  hundred  feet  and  care  is  taken  to  make  tests  of  potential 
to  earth  at  all  of  these  points,  the  presence  of  any  condition  which 
tends  to  cause  the  localized  flow  of  current  from  the  structure 
to  earth  will  usually  be  detected.  While  the  labor  of  making 
the  survey  is  increased  through  the  necessity  of  such  frequent 
observations,  it  is  preferable  to  include  all  accessible  points  in 
the  original  survey  and  to  eliminate  testing  points  in  subse- 


34  ELECTROLYSIS   SURVEYS 

quent  surveys  when  sufficient  experience  has  been  gained  to 
indicate  that  greater  distance  between  points  of  observation 
is  safe. 

When  the  electric  railways  in  the  area  under  investigation 
receive  current  from  two  or  more  sources  of  supply  and  there 
are  indications  that  electrolytic  damage  is  occurring  at  any 
point  upon  the  earthed  structures  investigated,  it  may  become 
necessary  to  ascertain  the  origin  of  the  current  causing  the 
injury.  The  preliminary  study  of  the  electric  railway  system 
or  systems  will  have  included  the  detailed  methods  for  distri- 
buting power,  whether  the  trolley  systems  are  interconnected 
or  divided  into  insulated  sections  and  whether  or  not  all  of  the 
rails  are  interconnected  at  junctions,  etc.,  as  well  as  the  methods 
of  bonding  and  cross-bonding.  If  the  trolley  is  supplied  from 
several  sources  in  parallel,  the  effect  of  any  one  of  these  upon 
the  distribution  of  stray  currents  may  most  easily  be  studied  in 
connection  with  the  starting  or  shutting  down  of  that  particular 
source.  When  substations  are  operated  only  during  part  of  -the 
day,  tests  may  be  arranged  to  take  advantage  of  this.  When 
the  substations  are  continually  in  operation,  resort  may  be  had 
to  the  method  of  simultaneously  observing  the  load  indicated  by 
the  station  instruments,  and  the  quantities  to  be  measured  on 
the  structure  being  surveyed.  Recording  instruments  are  often 
useful  for  this  purpose. 

When  the  sources  of  power  are  not  supplying  the  trolley 
in  parallel  but  are  confined  to  certain  definite  districts,  a  close 
study  of  the  railway  schedule  should  be  made  as  it  will  fre- 
quently be  possible  to  select  some  set  of  conditions  where  the 
current  at  points  of  observation  must  be  coming  almost  wholly 
from  one  of  the  sources  on  account  of  the  relative  positions 
of  cars,  etc.  Where  two  electric  railways  operate  independently 
without  connection  between  their  trolleys  but  with  inter- 
sections or  junctions  between  their  tracks,  the  situation  is 
similar  to  that  just  described  where  the  railway  trolley  is  divided 
into  insulated  sections  and  the  same  methods  of  investigation 
can  be  followed.  Where  there  is  no  connection  between  either 
trolleys  or  tracks  of  two  independently  operated  electric  rail- 
ways this  same  method  should  also  be  followed,  i.e.,  of  ob- 
serving stray  current  conditions  when  one  road  is  using  con- 
siderable current  in  the  immediate  neighborhood  and  the  other 
road  is  using  little  or  none  and  comparing  the  observations 
with  those  obtained  when  both  roads  are  using  normal  amounts 


ELECTROLYSIS   SURVEYS  35 

of  current  in  the  neighborhood.  It  is  to  be  noted  that  when 
two  railways  are  without  any  electrical  interconnections  be- 
tween either  trolleys  or  tracks,  the  track  return  of  either  may 
carry  stray  current  from  the  other  railway  and  if  the  track 
return  is  of  high  conductivity  it  may  assist  materially  in  pro- 
ducing adverse  electrolytic  conditions  on  other  earthed  struc- 
tures particularly  in  cases  where  it  provides  a  short  route 
between  two  points  between  which  considerable  potential  dif- 
ference exists. 

The  earth  ammeter,  previously  referred  to,  may  occasionally 
be  found  useful  in  checking  up  conditions  indicated  in  the 
systematic  survey  observations.  The  construction  of  the  de- 
vice is  described  in  the  apparatus  sections.  If  care  is  taken 
to  have  the  plates  placed  perpendicular  to  the  direction  of  cur- 
rent flow,  the  current  density  at  the  point  of  measurement 
may  be  indicated  by  the  current  flowing  through  the  instru- 
ment. If  necessary,  the  lines  of  current  flow  may  be  deter- 
mined by  voltage  readings  between  test  electrodes  before 
burying  the  instrument. 

The  greatest  care  should  be  taken  in  placing  the  instrument 
to  avoid  unnecessary  disturbance  of  the  soil,  in  order  that  the 
flow  lines  may  follow,  as  nearly  as  possible,  their  normal  direc- 
tions. 

Whenever  excavations  or  other  exposures  of  pipe  surfaces 
make  it  possible,  measurements  of  the  resistance  of  pipe  joints 
should  be  made.  Where  the  joints  are  of  moderate  resistance, 
that  is,  not  so  high  as  to  prevent  current  flow  upon  the  pipes, 
this  measurement  may  be  made  by  simultaneous  observations 
of  the  fall  of  potential  across  the  joint,  and  along  a  measured 
length  of  the  pipe ;  the  pipe  joint  resistance  may  then  be  expressed 
as  equivalent  length  of  pipe,  or,  by  reference  to  tables,  in  ohms. 
These  measurements  are  of  importance  in  indicating  the  char- 
acteristics of  the  pipe  line  as  an  electrical  conductor,  in  estimating 
the  probability  of  corrosion  at  joints  due  to  shunting,  etc. 

Wherever  the  surfaces  of  the  earthed  structures  under  in- 
vestigation are  exposed  during  the  course  of  the  tests,  their 
conditions  should  be  noted.  The  pitting  of  the  metal  surfaces 
or  the  presence  upon  them  of  rust  or  other  oxidation  products, 
or  an  obvious  reduction  in  the  thickness  of  the  metal  or  any 
other  evidence  that  corrosion  has  taken  place,  is  not  of 
itself  direct  evidence  that  electrolytic  corrosion  has  oc- 
curred. Corrosion  from  any  cause  whatever  would  be  expected 


36  ELECTROLYSIS   SURVEYS 

to  reduce  the  thickness  of  the  metal,  and  the  rate  at  which  such 
corrosion  occurred  and  its  possibilities  in  the  way  of  irregularity 
of  attack  on  different  portions  of  the  surface,  would  determine 
the  occurrence  of  pitting.  Many  of  the  products  of  corrosion 
which  will  be  encountered  can  also  be  produced  through  purely 
chemical  reactions,  as  well  as  by  electrolysis.  When  the  meas- 
urements made  in  the  survey  demonstrate  that  current  is  flow- 
ing from  structure  to  the  earth  at  the  point  where  corrosion  is 
observed,  conclusions  can  be  drawn  as  to  the  causative  relation 
between  the  presence  of  stray  current  and  the  evidences  of  cor- 
rosion. Whatever  the  conditions  found  in  the  survey  readings, 
the  condition  of  obviously  corroded  metal  surfaces  should  always 
be  carefully  noted,  as  it  is,  of  course,  always  possible  that  at  some 
past  time  stray  current  has  been  flowing  from  the  surfaces  to 
earth,  or  that  some  local  condition  has  been  favorable  to  the 
"  self -corrosion  "  of  the  structure.  Points  where  substantial 
corrosion  of  the  structures  under  investigation  is  found,  are 
always  to  be  regarded  as  good  locations  for  taking  the  samples 
of  soil  referred  to  in  the  following  paragraph. 

It  is  often  desirable  to  gather  data  relative  to  the  electrical 
and  chemical  characteristics  of  the  soils  in  the  area  studied.  As 
different  types  of  soil  are  encountered  in  the  course  of  the  survey 
either  in  the  making  of  excavations  or  through  the  observation 
of  changes  in  surface  conditions,  samples  should  then  be  taken 
and  their  electrical  conductivities  determined.  It  is  often 
desirable  also  to  make  chemical  analysis  of  a  number  of  samples 
of  ground  waters  and  of  the  water-soluble  portion  of  soil  samples 
secured  for  conductivity  tests. 

34.  Application    of    Remedial    Measures — Re-surveys.     The 

survey  methods  described  in  the  previous  paragraphs  include 
practically  all  of  the  work  which  would  be  done  in  an  extensive 
original  survey,  that  is,  in  a  district  where  no  work  had  been 
done  previously.  While  this  problem  in  all  of  its  aspects  has 
been  investigated  in  only  a  few  American  communities,  it  will 
be  found  that  more  or  less  complete  surveys  have  been  made  in 
almost  any  area  traversed  by  electric  railways. 

The  test  methods  described  are  not  all  of  equal  value  for  all 
problems;  their  application  depends  upon  the  particular  prob- 
lem under  consideration.  Further,  many  of  the  tests  require 
considerable  experience  and  technical  skill  in  application,  to 
avoid  erroneous  and  misleading  results.  For  these  reasons, 


ELECTROLYSIS   SURVEYS  37 

extensive  surveys  should  only  be  undertaken  by  experienced 
investigators. 

Following  the  completion  of  the  original  survey,  a  decision 
will  be  reached  as  to  whether  measures  for  mitigating  electro- 
lytic corrosion  are  necessary,  and  if  so,  what  methods  are  to  be 
applied.  Conclusions  as  to  the  effectiveness  of  any  protective 
measures  should  be  based  upon  repetitions  of  the  test  made  in 
the  orginal  survey.  The  amount  of  repetition  necessary  will 
depend  upon  the  character  of  the  protective  measures  adopted. 
Thus,  general  improvements  in  railway  return  circuits  will 
ordinarily  require  a  complete  re-survey  of  the  affected  area. 
The  instavlation  of  an  insulating  joint  between  the  main  line 
structure  and  a  branch  should,  on  the  other  hand,  require  little 
more  than  tests  over  short  sections  either  side  of  the  joint,  to 
determine  that  the  current  flowing  has  been  reduced  and  that 
no  objectionable  corrosive  conditions  have  been  introduced  at 
the  joint  itself. 

If  railway  return  circuits  are  being  changed,  some  observa- 
tions of  overall  potentials  and  potential  gradients  will  naturally 
be  made  during  the  course  of  reconstruction,  to  check  the  design 
upon  which  the  work  has  been  based.  Observations  should  be 
made  before  installing  drainage  systems  for  cables,  if  necessary 
using  available  conductors  temporarily  to  connect  the  cable 
sheath  and  the  railway  bus-bar  or  some  other  suitable  point 
on  the  railway  return,  and  the  effect  of  drawing  current  from 
the  cable  system  observed.  The  installation  of  such  protective 
measures  as  insulating  joints  or  insulating  coverings  should  be 
carefully  supervised  as  much  depends  upon  the  thoroughness 
with  which  the  work  is  done. 

In  re-surveys  after  the  installation  of  protective  measures, 
the  character  of  the  underground  structure  will  make  it  necessary 
to  pay  special  attention  to  some  particular  class  of  observations. 
With  piping  systems  and  power  distributing  cable  systems 
special  attention  should  be  given  to  the  amount  of  stray  cur- 
rent flowing  on  the  structures,  since  a  principal  object  of  the 
remedial  measures  will  have  been  a  reduction  in  this  current. 
When  insulating  joints  have  been  installed  tests  of  potential 
to  earth  from  each  side  of  the  joint  are  required  to  make  sure 
that  the  local  flow  of  current  to  earth  has  not  risen  to  an  amount 
which  will  endanger  the  structure.  Tests  of  stray  current  in  the 
system  on  either  side  of  the  joint  are  also  required  to  determine 
that  the  effect  desired  from  its  installation  has  been  obtained. 


38  ELECTROLYSIS   SURVEYS 

When  drainage  connections  are  attached  to  cable  systems,  tests 
of  potential  to  earth  must  be  made  throughout  the  area  affected. 
The  connection  should  make  the  cable  negative  to  earth  at  all 
points,  but  only  by  slight  amounts  at  or  near  the  point  of  its 
attachment,  as  otherwise  the  cable  will  carry  more  stray  current 
than  is  needed  for  its  protection,  and  it  becomes  a  source  of 
danger  to  other  un drained  structures. 

Where  insulating  joints  or  other  protective  measures  are  applied 
to  structures  buried  in  the  earth,  care  should  be  taken  to  attach 
testing  leads  to  be  used  in  future  surveys.  Such  connections 
will  be  of  the  same  general  type  as  the  current  measuring  leads 
for  pipes  (See  Fig.  1.). 

Electrolysis  surveys  should  be  repeated  at  suitable  intervals. 
In  case  the  original  survey  did  not  disclose  conditions  requiring 
the  application  of  remedial  measures,  it  is  still  necessary  to  make 
sure  that  adverse  conditions  have  not  since  arisen.  Where 
protective  measures  have  been  applied,  surveys  are  needed  to 
make  sure  that  the  remedies  remain  effective  and  adequate 
The  interval  between  surveys  will  depend  upon  the  importance 
of  the  structure  and  upon  the  time  required  to  produce  appre- 
ciable damage  in  case  a  substantial  change  in  stray  current 
conditions  occurred.  The  results  of  all  such  surveys  should 
always  be  compared  with  those  of  previous  surveys  to  ascertain 
whether  changes  in  stray  current  conditions  are  taking  place. 
When  any  substantial  changes  or  additions  are  made  in  the 
electric  railway  plant,  surveys  of  the  earthed  structures  liable 
to  be  affected  by  the  new  conditions  should  promptly  be  made. 

B:  APPARATUS. 

In  this  section  descriptions  are  given  of  the  apparatus  and  tools 
which  are  essentially  special  for  electrolysis  work.  The  tools 
ordinarily  used  for  handling  wires  and  making  good  contacts 
in  electrical  work  will  also  be  needed  but  no  special  description 
or  listing  of  them  seems  to  be  necessary  in  this  place. 

35.  Portable  Measuring  Instruments.  The  portable  measur- 
ing instruments  required  in  electrolysis  survey  work  include 
voltmeters,  milli voltmeters  and  ammeters.  Separate  instru- 
ments of  each  kind  can,  of  course,  be  carried  but  it  will  usually 
be  found  more  convenient  to  employ  the  special  portable  instru- 
ments which  have  been  designed  particularly  for  this  work. 


ELECTROLYSIS   SURVEYS  39 

Two  such  instruments  which  the  Weston  Electrical  Instrument 
Company  manufacture  for  this  class  of  work  are  as  follows : 

Model  1,  combination  millivoltmeter  and  voltmeter,  has 
its  zero  in  the  center  of  the  scale  and  reads  in  both  direc- 
tions. Ranges  of  5,  50  and  500  millivolts  and  of  5  and  50 
volts  are  convenient.  It  is  made  with  a  specially  high  resis- 
tance of  from  500  to  600  ohms  per  volt  so  that  the  5  milli- 
volt range  has  a  resistance  of  about  3  ohms.  These  high 
resistances  increase  the  accuracy  of  measurements  and  par- 
ticularly minimize  errors  due  to  resistances  of  leads  or 
contacts.  Ordinary  switchboard  shunts  provided  with 
binding  posts  and  adjusted  for  50  millivolts  may  be  used  to 
make  this  instrument  serve  as  an  ammeter.  Convenient 
ranges  for  these  shunts  in  electrolysis  work  are,  5,  50  and 
500  amperes. 

Model  56,  combination  volt-ammeter,  has  its  zero  in  the 
center  of  the  scale  and  reads  in  both  directions.  Ranges 
of  10,  50  and  500  miUivolts,  5  and  50  volts  and  100  amperes 
are  convenient. 

The  center  scale  feature  referred  to  in  the  description  of  these 
instruments  is  an  important  one  in  electrolysis  work,  as  it  is  not 
always  possible  to  determine  in  advance  the  direction  of  current 
or  potential,  and  readings  may  also  vary  from  positive  to  nega- 
tive values  during  the  making  of  observations  at  many  testing 
points.  When  simultaneous  readings  have  to  be  taken  at  two 
or  more  testing  points  it  is  important  to  use  similar  instruments 
at  all  points.  If  dissimilar  instruments  are  used  their  periods 
of  vibration  may  differ  and  with  the  fluctuating  voltages  and 
currents  encountered  in  much  of  this  work  accurate  simultaneous 
measurements  cannot  be  made  unless  the  instruments  used  have 
the  same  periods  of  vibration. 

36.  Recording  Instruments.  Recording  measuring  instru- 
ments are  usually  arranged  to  give  24-hour  records  without 
change  of  chart.  By  using  a  sensitive  millivoltmeter  in  the 
recording  instrument  and  providing  it  with  a  number  of  voltage 
ranges  as  well  as  with  suitable  shunts,  a  single  instrument  can  be 
made  available  for  taking  all  of  the  voltage  and  current  readings 
required  in  electrolysis  work.  The  original  type  of  Bristol 
recording  instruments  make  their  records  upon  a  smoked  chart 
which  has  to  be  treated  subsequently  with  a  fixative  supplied 
with  the  instrument  in  case  it  is  desired  to  preserve  the  record. 
The  Bristol  instruments  are  regularly  made  with  a  clock 
supplied  with  a  changing  lever  so  that  the  disc  can  be  made  to 


40  ELECTROLYSIS   SURVEYS 

rotate  either  in  one  hour  or  twenty-four  hours.  Both  the  Bristol 
Company  and  the  Esterline  Company  have  recording  instruments 
which  give  an  ink  record  on  a  paper  strip.  In  either  type  of 
instrument  center  scale  zeros  should  be  called  for  so  that  varia- 
tions between  positive  and  negative  values  will  be  recorded  on 
the  chart. 

37.  Normal   Electrode.     The    Haber   normal   electrode    also 
called  non-polarizable  electrode  consists  of  a  rod  of  zinc  which 
is  enveloped  in  a  wet  paste  of  zinc  sulphate  contained  in  a  glass 
tube  which  has  had  cemented  to  it  at  the  bottom  a  porous  clay 
cell.     The  other  end  of  the  tube  is  closed  with  a  stopper  from 
which  the  zinc  rod  is  supported  an  insulated  wire  is  led  from  the 
end  of  the  zinc  rod  through  this  stopper  to  the  upper  end  of  a 
wooden  rod  which  also  enters  the  stopper  and  serves  for  the 
purpose  of  handling  the  electrode.     A  capillary  tube  is  also  run 
through  the  stopper  in  order  to  have  the  interior  of  the  tube  at 
normal  atmospheric  pressure.     The  zinc  sulphate  paste  is  made 
by  adding  saturated  zinc  sulphate  solution  to  fine  zinc  sulphate 
crystals  until  the  mixture  has  attained  a  semi-fluid  condition. 
A   sketch   showing   details   of   construction   for   this    device   is 
shown  on  the  opposite  page.     (See  Fig.  2.) 

38.  Earth  Ammeter.     The  Haber  earth'  ammeter  consists  of 
two  thin  copper  sheets  laid  one  upon  the  other  with  a  thin  sheet 
of  mica  or  other  non-absorbent  insulating  material  between  them. 
These  two  plates  are  gripped  in  a  hard  rubber  rim  which  forms 
part  of  a  square  wooden  frame.     A  paste  made  by  mixing  pow- 
dered copper  sulphate  crystals  with  a  20%  aqueous  solution  of 
sulphuric  acid  is  spread  over  the  exterior  surfaces  of  each  of  the 
two  sheets  of  copper,  the  paste  being  enclosed  on  each  exterior 
surface  by  a  covering  of  parchment  paper  or  some  similar  tough 
permeable  membrane.     Insulated  wire  leads  of  suitable  length 
are  run  from  each  plate  through  the  frame  to  connect  with  the 
measuring  instrument.     The  opening  in  the  frame  may  conven- 
iently be  square.     Four  inches  is  a  convenient  dimension  for  the 
sides  of  this  square  opening  as  this  will  yield  an  area  of  one-ninth 
of  a  square  foot  which  is  approximately  equivalent  to  a  square 
decimeter.     The    detailed    construction    of    the    instrument    is 
shown    in    an    attached    sketch.     (See    Fig.    3.)      When  using 
the    instrument,    the    spaces    between    the    parchment    paper 
and  the  outer  edges  of  the  wooden  frame  are  first  filled  with 


ELECTROLYSIS   SURVEYS 


41 


SECTION  OF 
NON-POLARIZABLE  ELECTRODE 


Insulated 

Copper  wire 


Zinc  Rod 


(r 


Glass  Tube  — 


Wooden  Rod, 3 'Long 


Capillary  Tube 
Rubber  Stopper 


^_Hooksfor  Binding 
Wire  to  hold  5  topper 


Zinc  Sulphate  Paste 


Clay  Porous  Cup 


Resin  Cement 


cm. 


CROSS  SECTION 

Figure  2 


42 


ELECT ROL  YSIS   S UR  VE  YS 


SECTION  OF  EARTH  AMMETER 

Ammeter  Leads 


wooden  Frame - 
Copperplate 

GopperSulphate  Paste 
Earth  - 

Wooden  Frame - 


Hard  Rubber  Frame 

Copperplate 

(Sheet  oFMica 
[separating  Plates 

Parchment  Paper 


Hard  Rubber  Frame 


CROSS  SECTION 

Figure  3 


ELECTROLYSIS   SURVEYS  43 

closely  packed  soil  taken  from  the  spot  where  it  is  intended  to 
make  the  measurement  and  the  frame  is  then  placed  in  a  position 
perpendicular  to  the  flow  of  current  which  it  is  desired  to  measure 
and  completely  buried  in  earth  removed  in  the  course  of  making 
the  excavation  to  reach  the  structure  whose  condition  is  to  be 
determined.  A  suitable  low  resistance  milliammeter  can  then 
be  connected  to  the  two  terminal  wires  and  observations  of  the 
current  flowing  made. 

39.  Testing  Electrodes.     The  details  of  metal  tipped  testing 
electrodes  for  use  in  readings  of  potential  to  earth  are  given  in 
an    attached    sketch.      (See   Fig.   4.)     Two    of    these    testing 
rods  may  be  conveniently  carried  at  all  times;  one  of  the  two 
should  have  as  its  testing  tip  a  piece  of  the  same  metal  as  that 
contained  in  the  structure  whose  potential  to  earth  is  to  be  tested, 
the  other  should  be  provided  with  a  steel  tip  so  that  contact  may 
be  maintained  from  a  distance  with  any  pipe  or  cable  which  is 
below  the  surface  of  the  ground.     The  metal  on  the  tips  of  these 
rods  should  always  be  kept  clean  and  bright  and  care  should  also 
be  taken  to  remove  rust  and  other  products  of  corrosion  from  the 
points  on  the  surface  of  the  structure  to  be  tested  against  which 
the  steel  tip  presses  so  that  a  clean,  bright  surface  will  be  available 
for  the  contact. 

C:  RECORDS  AND  REPORTS. 

40.  General.  Much  detailed  information  is  necessarily  gathered 
in  the  course  of  an  electrolysis  survey.     It  is  desirable  to  prepare 
in  advance  of  the  work  for  the  convenient  recording  of  these  data 
upon  suitably  arranged  testing  sheets,  which  either  have  upon 
one  line  or  upon  one  sheet,  as  may  be  necessary,  all  of  the  data 
collected  at  any  stated  testing  point  during  a  single  period  of 
observation.     Several  typical  data  sheets  prepared  for  recording 
observations  made  upon  piping  and  cable  systems  are  attached 
hereto  as  suggestive  of  possible  arrangements  for  report  sheets. 
The  data  thus  collected  can  usually  be  best  aranged  for  study 
if  they  are  transferred  to  a  map  showing  the  system  or  systems 
included  in  the  tests,  and  indicated  thereon  either  in  numerical 
form  or  through  some  graphical  representation.     It  is  desirable 
to  indicate  positive  and  negative  relations  by  making  records 
on  the  maps  in  different  colors. 

Apart  from  the  data  obtained  through  observations  in  the 


ELECTROLYSIS   SURVEYS 


V----J 


ELECTROLYSIS   SURVEYS  45 

work  of  the  electrolysis  survey  it  will  be  seen  that  the  records 
obtained  relating  to  the  systems  under  observation  should 
include  the  following: 

41.  Electric  Railways. 

1.  Maps  showing  locations  of  sources  of  power  supply, 
tracks,  and  negative  feeders  and  other  connections  between 
bus-bar  and  track.    Also  locations  of  positive  feeding  connec- 
tions to  trolley  and  of  all  section  insulators  in  trolley. 

2.  Information  as  to  size  of  rails,  methods  of  bonding  and 
standards  of  bond  maintenance. 

3.  Information  as  to  any  direct  ground  connections  ap- 
plied to  the  railway  return  system,  and  any  special  track 
features  which  may  affect  the  flow  of  stray  currents. 

42.  Piping  Systems. 

1.  Maps  showing  all    main    piping   lines    and    branches 
(except   building  connections)   and  sources  of  water,   gas, 
etc.,  from  which  the  piping  systems  are  supplied. 

2.  Information  as  to  sizes  of  pipes  and  metals  of  which 
they  are  composed,  and  details  of  the  standard  methods  of 
joining  main  and  branch  line  pipe  sections. 

3.  Information  as  to  method  of  joining  building  connec- 
tions to  main  supply  pipes  including  metals  used  for  the 
building  connection  pipes   and  the  depth  to  which  such 
connections  are  buried. 

4.  Location   and  description,  of  any  protective  devices 
such  as  insulating  joints  or  drainage  connections  which  may 
have  been  made  a  part  of  the  piping  system. 

5.  Information  as  to  methods  of  attachment  and  con- 
struction employed  in  carrying  pipes  over  highway  or  rail- 
way bridges  or  under  water  courses,  swamps,  etc. 

43.  Cable  Systems. 

1.  Maps  showing  locations  of  all  subway  and  conduit  routes 
and  giving  number  and  sizes  of  cables  in  place  therein  or 
the  total  cross-section  of  lead  sheaths  expressed  in  equiva- 
lent copper,    also  locations  of  power  stations,  sub-stations  or 
other  centers  from  which  cables  radiate. 

2.  Locations,  route  and  sizes  of  all  drainage  connections 
attached  to  cable  systems,  also  locations  of  all  insulating 
joints  in  cable  systems,  of  any  jumpers  which  may  be  run 
to  establish  a  metallic  circuit  across  an  insulated  gap  in  the 
cable  system  and  of  any  conductors  run  to  reinforce  the 
carrying  capacity  of  the  cable  system  for  stray  currents. 

3.  Information  as  to  methods  of  attachment  and  con- 
struction  employed   in   carrying   cables   over   highway   or 
railway  bridges  or  under  water  courses,  swamps,  etc. 


46  ELECTROLYSIS   SURVEYS 

44.  Bridges  and  Buildings. 

1.  Locations  of  structures  with  respect  to  electric  railways. 

2.  Information  as  to  methods  of  construction  employed 
in  carrying  electric  railway,  pipes  and  cables  across  bridges 
and  particularly  as  to  whether  any  of  these  other  structural 
systems  make  electrical  contact  with  the  metal  structure 
of  the  bridge. 

45.  General  Conditions. 

1.  Maps  showing  locations  of  water  courses,  swamps  and 
other    features   tending    to    produce   locally  earth  of  high 
unit  conductivity. 

2.  Records  of  electrical  resistance  of  soil  samples  repre- 
sentative of  the  area. 

3.  Records  of  experience  obtained  in  the  use  of  different 
metals  for  pipes,  etc.,  in  the  soils  o'f  the  area. 

It  is  desirable  that  in  the  preparation  of  records  and  of  reports, 
consideration  be  given  to  the  necessity  of  their  perpetuation.  All 
records  which  will  be  of  permanent  value  in  connection  with  the 
continued  study  of  electrolysis  conditions  within  the  area  which 
will  be  necessary  in  order  to  make  sure  that  injurious  changes 
in  conditions  do  not  occur,  should  be  prepared  in  a  permanent 
form  capable  of  withstanding  considerable  handling. 


AMERICAN   PRACTICE  47 


III.    AMERICAN  PRACTICE. 

There  is  no  standard  practice  in  the  treatment  of  elec- 
trolysis problems  in  America.  In  many  localities  the  exist- 
ence of  such  a  problem  is  scarcely  recognized;  in  others  the 
problem  has  been  given  much  study,  and  mitigating  systems 
widely  varying  in  character  have  been  installed. 

Much  of  the  information  made  available  to  the  committee 
is  contained  in  confidential  reports  to  which  it  is  not  possible 
to  make  reference,  because  electrolysis  is  the  subject  of  con- 
troversy between  conflicting  interests.  Unfortunately,  also  it 
is  impossible  in  some  cases  even  to  refer  to  places  where  par- 
ticular expedients  have  been  employed,  or  to  state  either  the 
extent  or  the  results  of  such  use.  It  has,  therefore,  been  neces- 
sary in  most  instances  to  make  statements  of  what  is  the  prac- 
tice, without  citing  the  authority  or  naming  the  places  where 
such  practice  may  be  found.  In  compiling  this  report,  there- 
fore, the  committee  has  been  influenced  most  largely  by  those 
instances  of  practice  within  its  knowledge  where  the  greatest 
amount  of  study  has  been  given  to  the  subject,  and  where  the 
results  obtained  seem  best  to  justify  its  use.  The  committee 
has  embodied  in  this  report  only  matters  of  fact  for  which  it 
has  authority. 

A.     MEASURES  APPLIED  TO  RAILWAYS.   - 

46.  Insulation.  Under  this  sub-heading  have  been  con- 
sidered three  general  measures,  namely:  a.  Complete  Insula- 
tion, which  does  not  involve  the  use  of  the  running  rails  as  a 
portion  of  the  electric  circuit,  b.  Substantial  Insulation,  which 
does  involve  the  use  of  the  running  rails  as  a  portion  of  the 
circuit,  but,  due  to  the  type  of  construction  employed,  to  a 
very  large  extent  prevents  stray  currents,  and  c.  Partial  In- 
sulation, which  comprises  using  such  means  as  are  available 
to  insulate  the  running  rails  of  ordinary  street  railways  in  so  far 
as  practicable. 


48  AMERICAN   PRACTICE 

(a)  Complete  Insulation.     Instead  of  using  the  running  tracks 
as  part  of  the  return  circuit,  a  separate  insulated  return  con- 
ductor is  employed  for  this  purpose.     In  this  case  the  entire 
electric  circuit  of  the  railway  system  is  insulated  from  ground, 
and,  there  being  no  voltage  drop  in  contact  with  earth,  stray 
currents  are  entirely  prevented.      Complete   insulation   of  the 
railway    circuit    is    accomplished    in   the   double   underground 
conduit  trolley  system,    by   employing   insulated  positive  and 
negative   conductors  in  underground   conduits.      This    system 
is  in  use  on  the  surface  lines  on  Manhattan  Island  and  in  por- 
tions of  Washington,   D.  C.     This  is  also  accomplished  in  the 
double  overhead  trolley  system  by  employing  separate  positive 
and  negative   overhead  trolley  wires  insulated  from   ground; 
many   years    ago    examples    of  this  system  were    installed    in 
Washington,  D.  C.,  and  Cincinnati,  Ohio.     The  practice  while 
effective  in  this  respect  and  in  use  for  a  long  term  of  years  has 
not  spread  to  other  cities  possibly  because  of  the  unsightly  ap- 
pearance of  the  overhead  structures  due  to  the  multiplicity  of 
wires  and  because  of  the  increase  in  operating  difficulty  and  ex- 
pense which  it  entailed. 

(b)  Substantial  Insulation.     Interurban  and  electrified  steam 
roads  generally  require  the  rails  to  be  supported  on  wooden  ties 
set  in  well  drained  broken  stone  or  gravel  ballast.     The  insulation 
afforded  by  such  construction  practically  removes  danger  from 
electrolysis.     Leakage  is  in  some  instances  found  to  be   as   low 
as  .00016  ampere  per  rail  per  tie  under  dry  weather  conditions, 
increasing  to  .0055  ampere  when  wet  with   10  volts  between 
the  rail  and  ground.     On  steel  structures  where  the  ties  are 
only  partially  in    contact    with    ground    and    the    ties    cannot 
become  waterlogged,  this  leakage  is  even  less.     The  substantial 
insulation  of  a  ballasted  roadbed  has,  in  some  installations, 
been  rendered   ineffective   by   bare   negative   cables   in   damp 
earth  or  by  metallic  connections  between  the  tracks  and  steel 
supporting    construction.     Conditions    are    found    to    be    very 
favorable  for  rail  insulation  where  the  tracks  are  in  subways 
or  under   cover   protected  from  the  weather,   permitting  the 
ballast  and  ties  to  become  permanently  dry. 

(c)  Partial   Insulation.     The   escape   of  current  from  tracks 
largely  buried  is  decreased  by  high  contact  resistances  between 
the  tracks  and  the  surrounding  medium.     The  total  resistance 


AMERICAN   PRACTICE  49 

to  flow  of  escaping  current  is  found  to  vary  with  the  earth 
resistance  and  the  contact  resistance  between  earth  and  rail. 
Since  the  earth  resistance  is  usually  low,  the  contact  resistance 
is  generally  found  to  be  the  controlling  factor  in  the  leakage 
path;  hence,  partial  insulation  is  found  effective  in  reducing 
leakage  with  the  low  voltages  commonly  encountered.  On  a 
grounded  trolley  system  in  city  streets  it  has  been  found  bene- 
ficial to  have  the  rails  as  nearly  enclosed  with  insulating  material 
as  possible. 

47.  Reduction  of  Track  Voltage  Drop. 

(a)  Bonding.  The  best  types  of  solid  rail  joints  in  actual  use 
give  the  same  electrical  conductivity  at  the  joint  as  in  any 
other  part  of  the  rail  length.  The  standard  of  good  practice 
in  some  electrified  steam  roads  is  that,  the  resistance  through 
the  rail  joint  shall  be  equivalent  to  that  of  a  20-inch  length  of 
the  rail  adjacent,  and  should  the  resistance  exceed  42  inches, 
that  the  bond  should  be  remade.  With  respect  to  the  practice 
of  bonding  in  street  railway  systems,  it  may  be  said  that  there 
is  no  standard  equivalent  length  of  rail  to  cover  all  conditions, 
but  each  railway  company  establishes  its  own  standard,  de- 
pending on  local  conditions.  The  equivalent  resistance  of  the 
rail  joint  in  terms  of  length  of  rail  will  depend  on  the  length 
and  size  of  the  bond,  the  terminal  contact  resistance  and  the 
conductivity  of  the  rail.  In  large  cities  bonding  to  an  equivalent 
resistance  of  from  three  to  six  feet  of  rail  is  common  practice. 
In  suburban  districts  higher  bond  resistances  are  often  used.  The 
equivalent  resistance  of  rail  joint  which  is  adopted  by  different 
railroads  necessarily  varies  widely  with  the  condition  of  load 
and  class  of  bond  employed.  The  class  of  bond  chosen  is  in  many 
cases  determined  by  mechanical  conditions,  such  as  the  founda- 
tion upon  which  the  track  is  laid. 

Bonds  are  generally  classified  according  to  the  method  of 
fastening  them  to  the  rail.  Soldered  bonds  are  soldered  to 
the  head,  base  or  web  of  the  rail.  Pin  expanded  bonds  have 
holes  drilled  in  their  terminals,  through  which  a  steel  pin  is 
driven  to  expand  the  terminal  into  a  hole  drilled  in  the  rail. 
After  expansion  a  steel  cylindrical  plug  is  driven  in  the  expanded 
hole  to  prevent  contraction.  Brazed  or  welded  bonds  are  attached 
to  the  rail  by  heat  generated  electrically  or  by  an  oxy-acetylene 
flame  applied  to  the  terminal  of  the  bond.  Compressed  terminal 
bonds  and  compressed  multiple  terminal  bonds  have  their  term- 


50  AMERICAN   PRACTICE 

inals  formed  into  a  solid  cylindrical  stud,  or  studs,  and  are 
compressed  in  the  rail  holes  with  screw  or  hydraulic  com- 
pressors or  by  hammer  blows,  which  expand  the  studs  in  threaded 
or  beaded  holes  of  the  rail.  A  special  type  of  this  bond  has 
large  contact  surfaces  about  the  terminal,  so  that  the  bonds 
can  be  soldered  and  compressed  to  the  rail. 

The  carrying  capacity  of  bonds  has  sometimes  been  found 
insufficient  to  keep  their  temperature  within  safe  limits  under 
conditions  of  maximum  load  where  bonds  involving  soldered 
joints  are  used.  The  resistance  of  a  rail  joint  is  found  to  be 
affected  largely  by  the  contact  resistance  between  the  bond 
terminals  and  the  rail.  Good  contact  and  large  surface  of 
contact  at  the  bond  terminals  are  found  necessary  to  low  joint 
resistance.  Replacement  of 'bonds  is  generally  made  necessary 
by  depreciation  at  the  contacts,  the  breaking  of  strands  by 
vibration  or  by  mechanical  injury. 

There  are  now  in  general  use  several  different  types  of  rail 
joints  which-  render  additional  bonding  unnecessary.  Among 
•these  types  of  rail  joints  are  the  following:  Cast  Welded:  The 
rails  are  connected  together  by  pouring  molten  iron  into  a 
mold  that  surrounds  the  joint,  and  when  the  metal  cools  the 
joint  is  rigid  and  of  low  electrical  resistance.  Thermit  welding 
is  another  example  of  this  method,  the  iron  being  liberated  at 
a  white  heat  from  a  mixture  of  iron  oxide  and  aluminum  which 
is  ignited  in  a  crucible.  Electrically  Welded:  Iron  splice  plates 
are  electrically  welded  to  the  rail.  Nichols  Zinc  Joints:  This 
joint  is  made  by  pouring  molten  zinc  between  the  fish  plates  and 
the  rail  ends.  The  zinc  is  poured  in  after  the  fish  plates  are  bolted 
on,  and  the  expansion  of  the  zinc  in  solidifying  is  relied  upon 
to  make  a  contact  between  the  fish  plates  and  rail  ends  which 
is  reported  to  be  permanent.  Romapac  Continuous  Rail: 
The  rail  consists  of  two  pieces  which  are  so  laid  that  the  rail 
head  joint  and  the  rail  base  joint  are  staggered,  then  the  rail 
head  is  rolled  or  crimped  on  to  the  rail  base  thus  forming  a 
continuous  electrical  path. 

(b)  Cross-bonds  are  electrical  conductors  for  equalizing  the 
current  flow  in  the  rails.  When  the  roadbed  is  dry  they  are 
usually  installed  bare  in  the  ground.  Insulated  cable  is,  how- 
ever, sometimes  used,  and  the  insulation  is  protected  by  a  heavy 
braid  or  circular  loom  tubing. 

The  important  objects  of  cross-bonding  are  to  equalize  the 


AMERICAN   PRACTICE  51 

current  flow  between  rails  and  to  insure  continuity  of  the  return 
circuit  in  case  of  a  broken  rail  or  bond  in  any  one  rail.  It  is 
usual  practice  on  suburban  railways  to  place  cross-bonds  at 
intervals  of  1,000  to  2,000  feet  and  at  shorter  spacing,  some- 
times as  low  as  300  feet  on  street  railways.  Cross-bonding 
between  parallel  tracks  is  in  some  cases  installed  with  the 
same  frequency  as  between  the  rails  of  the  single  track;  in 
other  cases  at  less  frequent  intervals. 

In  determining  the  location  of  cross-bonds  in  connection  with 
alternating  current  single  track  signal  circuits,  a  departure  from 
ideal  spacing  becomes  necessary,  owing  to  the  fact  that  cross- 
bonds  are  permissible  only  at  the  reactance  bonds.  The  signal 
reactance  bonds  are  located  between  the  signal  block  sections, 
and  these  sections  are  more  or  less  fixed  for  train  operating 
conditions.  The  general  method  used  under  these  conditions 
is  to  cross-bond  at  all  signal  reactance  bonds  and  install  addi- 
tional cross-bonds  with  reactance  bonds  at  intermediate  loca- 
tions to  obtain  the  most  satisfactory  resistance  conditions  in 
the  sections  fixed  by  the  signal  system. 

The  common  practice  of  electrified  steam  railroads  is  to  use 
cross-bonds  with  a  conductance  equal  to  one  track  rail,  or 
about  1,000,000  circular  mils.  Street  and  interurban  railways 
employ  copper  having  a  cross-section  of  from  200,000  to  500,000 
circular  mils. 

Some  companies  provide  jumpers  at  switches,  frogs  and  at  other 
special  track  work,  to  insure  that  the  electrical  continuity  of 
the  bonded  rail  will  be  maintained.  This  is  usually  accom- 
plished by  jumpers  extending  around  the  special  work,  except 
where  broken  rail  signal  protection  is  required,  and  in  such 
cases  the  frogs  are  bonded  in  the  return  current  system.  In 
recent  practice  these  jumpers  are  made  of  insulated  copper 
cables,  except  in  dry  locations,  as,  for  instance,  in  permanently 
dry  rock  ballast,  or  on  elevated  structures  with  wooden  ties 
and  no  ballast,  the  cables  being  kept  clear  of  the  steel  structure. 
The  electrical  leakage  from  a  bare  negative  jumper  in  damp 
earth  has  been  known  to  offset  the  effect  of  many  miles  of  most 
careful  track  insulation.  Under  such  conditions  the  bond  is 
gradually  destroyed  by  electrolysis. 

(c)  Conductivity  and  Composition  of  Rails.  The  conductivity 
of  the  track  rails  used  by  several  interurban  and  electrified 
steam  railroads  has  been  found  to  be  equivalent  to  about  1/12 


52  AMERICAN   PRACTICE 

that  of  copper,  and  this  figure  generally  holds  approximately 
true  for  girder  types  of  rails,  except  when  alloy  steel  is  used, 
in  which  case  higher  resistances  are  found.  The  track  rails 
are  specified  for  their  mechanical  qualities,  and,  where  these 
interfere  with  the  electrical  requirements,  it  is  customary  to 
give  the  mechanical  qualities  preference.  The  composition  of 
rails  for  heavy  service  used  by  one  of  the  large  electrified  steam 
railroads,  in  percentages,  is  as  follows: 

Carbon 0.62  to  0.75 

Manganese 0.  70  to  1 . 00 

Silicon 0.10  to  0.20 

Phosphorus .  .  not  to  exceed  0 . 04 

The  American  Electric  Railway  Engineering  Association  has 
adopted  the  following  standard  composition  for  heavy  service 

rails : 

Class  A  Rails  Class  B  Rails 


Carbon 0.60  to  0.75  0.70  to  0.85 

Manganese 0.60  to  0.90  0.60  to  0.90 

Silicon . Not  more  than  0 . 20  Not  more  than  0 . 20 

Phosphorus Not  more  than  0.04  Not  more  than  0.04 

d.  Reinforcement  of  Rail  Conductivity.  Early  track  con- 
struction practice  in  this  country  often  included  bare  wire 
laid  between  the  rails  and  connected  to  each  bond.  Some- 
times '  one  such  wire  was  used  for  each  rail ;  sometimes  one 
for  each  track,  and  sometimes  one  served  for  a  double 
track.  The  wires  varied  from  No.  4  to  No.  1,  and  were  either 
of  copper  or  galvanized  iron.  Their  conductivity  was  small 
and  they  were  subject  to  electrolytic  injury  and  frequent  break- 
age. This  construction  has  practically  gone  out  of  use.  It 
is,  however,  common  to  find  the  rails  supplemented  in  the  vi- 
cinity of  supply  stations  by  large  conductors  connected  in  par- 
allel to  the  rails.  This  is  not  infrequently  done  by  the  use  of 
bare  copper  wire  or  cable  buried  between  rails,  and  hence  in 
full  contact  with  the  earth.  Old  rails,  bolted  and  bonded  to- 
gether and  buried  beneath  or  beside  the  track,  have  also  been 
used  in  some  cases. 

Buried  bare  conductors,  however,  increase  the  contact  area 
between  the  return  circuit  and  the  earth,  and  the  tendency  to 
augment  stray  currents  thus  caused  off  sets,  to  a  greater  or  lesser 
extent,  the  benefits  attained  by  the  reduction  of  drop.  The 


AMERICAN   PRACTICE  53 

benefits  to  be  derived,  therefore,  from  an  electrolysis  stand- 
point, may,  if  use  is  made  of  bare  conductors  buried  in  the 
earth,  be  open  to  question.  The  direct  benefits  that  accrue 
from  the  practice  of  reinforcing  the  conductivity  of  the  rail, 
listed  in  what  may  be  considered  their  order  of  importance,  are : 
(1)  Reduction  of  energy  losses;  (2)  The  maintenance  of  a  higher 
average  voltage  at  the  cars,  especially  at  times  of  peak  load,  thus 
resulting  in  improved  car  service  and  car  lighting;  and  (3) 
The  reduction  in  potential  drop  in  the  rails,  thus  reducing  stray 
currents  and,  in  turn,  therefore,  lessening  the  damage  to  the 
extent  that  these  stray  currents  are  reduced,  qualified,  how- 
ever, in  accordance  with  the  statement  previously  made  if 
buried  bare  conductors  are  used. 

Where  conductors  paralleling  the  rails  are  installed  as  an 
electrolysis  mitigation  measure,  they  are  usually  insulated 
from  earth  by  carrying  them  overhead  or  in  underground 
conduit.  The  practice  varies  as  to  the  method  of  connecting 
such  conductors  to  the  rail;  they  are  sometimes  connected  at 
the  ends  only  but  more  generally  at  intermediate  points  also. 
Where  this  arrangement  is  used  the  track  rails  are  connected 
to  the  negative  bus  at  the  nearest  convenient  point. 

Conductors  are  here  regarded  as  in  parallel  with  the  rails 
when  one  end  is  connected  to  the  track  and  the  other  to  a 
station  bus-bar  which  is  connected  directly  to  the  rail  by  a 
conductor  of  negligible  resistance.  The  use  of  such  conductors 
should  not  be  confused  with  the  "Insulated  Track  Feeder 
System,"  which  has  for  its  prime  object  the  mitigation  of 
electrolysis.  This  is  treated  under  a  subsequent  heading. 

(e.)  Use  of  Additional  Power  Supply  Stations  and  Distri- 
bution of  Load.  The  growth  of  electric  railway  systems  in 
large  cities  has  often  led  to  the  installation  of  additional  power 
stations  or  substations  for  the  more  economical  and  satis- 
factory operation  of  the  railroad.  This  has  also  reduced  the  track 
voltage  drop  and  subdivided  the  areas  over  which  leakage 
from  rail  to  earth  occurs  and  thus  has  had  the  effect  of  reducing 
the  stray  currents. 

The  effect  of  providing  additional  centers  of  power  supply 
can  best  be  illustrated  by  the  curves  on  Figure  5,  which,  while 
deduced  from  theory,  illustrate  in  a  simple  case  effects  such 
as  have  been  observed  in  practice. 

The  curve  SAO  of  Figure  5  represents  the  track    voltage 


54 


AMERICAN   PRACTICE 


REDUCTION  OF  TRACK  VOLTAGE   DROP   BY 
ADDITIONAL    POWER    SUPPLY  STATIONS 


DISTANCE 


Figure  5 


AMERICAN   PRACTICE  55 

drop  on  a  portion  of  an  electric  railway  system  having  a  uni- 
formly distributed  load.  This  curve  is  a  parabola  with  a 
vertical  axis  and  with  the  apex  at  0 — that  is,  at  the  end  of  the 
line. 

The  curve  SB F  illustrates  the  condition  of  a  substation  lo- 
cated at  P  (33  per  cent  of  the  distance  from  Q  to  S)  carrying 
20  per  cent  of  the  total  load.  In  this  curve  the  portion  BF 
is  identical  with  AO.  As  the  load  is  uniformly  distributed, 
33  per  cent  of  the  load  is  on  the  portion  of  the  line  shown  by 
PQ,  and  of  this  33  per  cent,  20  per  cent  is  carried  by  the  sub- 
station P.  The  remainder,  or  13  per  cent,  is  carried  by  the 
station  S.  The  point  B  on  the  curve  SBF,  therefore,  corresponds 
to  the  point  N  on  the  curve  SAO,  the  distance  QR  being  13  per 
cent  of  QS. 

In  the  same  manner  the  curves  SCG,  SDH  and  SEK  are 
drawn  showing  the  conditions  when  the  station  P  carries  40 
per  cent,  60  per  cent  and  80  per  cent,  respectively,  of  the 
total  load.  The  summit  of  the  curve  SMD,  in  which  .the 
station  P  carries  60  per  cent  of  the  load,  is  located  so  that  PL 
equals  60  per  cent  minus  33  per  cent,  or  27  per  cent  of  the  total 
length  SQ  to  the  left  of  P.  The  distance-  QL  is,  therefore,  60 
per  cent  of  the  total  length  QS. 

In  general,  the  conditions  are  more  complicated  than  those 
here  assumed,  and  will  ordinarily  prevent  an  accurate  deter- 
mination of  the  relative  location  of  the  negative  busses  of  the 
two  stations.  It  is  possible,  however,  to  make  tests  which 
will  verify  each  of  the  points  which  have  been  used  in  preparing 
the  curves,  although  it  may  not  be  possible  to  verify  all  of  them 
at  any  one  test  or  in  one  location. 

48.  Three-wire  Systems.  As  far  back  as  1894,  and  possibly 
earlier,  consideration  was  given  to  a  three-wire  system  of  opera- 
tion for  electric  street  railways,  wherein  the  tracks  acted  as 
the  neutral  circuit.  The  reason  for  considering  such  a  system 
was  to  reduce  stray  currents  through  the  earth.  Installations 
of  this  sort  were  tried  out  in  Pittsburgh,  Pa.,  Lowell,  Mass., 
Portland,  Ore.,  and  Seattle,  Wash.,  in  the  earlier  days;  some- 
what later  an  experimental  installation  was  made  in  Cambridge, 
Mass.  In  the  Transactions  of  the  American  Institute  of  Elec- 
trical Engineers  for  1907,  Vol.  XXVI,  No.  1,  pages  268  to  280, 
Messrs.  Paul  Winsor  and  J.  W.  Corning  report  the  results  of 
an  investigation  to  determine  the  feasibility  of  using  the  three 


56  AMERICAN   PRACTICE 

wire  system  for  the  purpose  of  reducing  stray  currents  through 
the  earth.  This  investigation  showed  that  the  three- wire 
system  of  operation  materially  reduced  the  track  voltage  drop, 
and  therefore  reduced  the  amount  of  stray  current  in  the  earth 
and  in  underground  metallic  structures.  The  figures  and  curves 
shown  by  Mr.  Corning  indicate  that  there  is  a  reduction  in  current 
flowing  on  pipe  lines  tested  by  him  of  the  order  of  nearly  90 
per  cent. 

Until  very  recently  it  was  thought  that  three-wire  systems 
contained  certain  serious  inherent  disadvantages.  It  was  felt 
that  the  complications  in  machinery,  difficulties  in  successfully 
insulating  trolleys  of  different  polarities,  difficulties  in  equalizing 
the  load  between  different  sections,  and,  fuither,  the  necessity 
for  the  installation  of  larger  generating  units  to  compensate  for 
the  difficulties  in  balancing  than  were  required  with  the  single- 
trolley  grounded  system,  were  so  great  as  to  preclude  the  con- 
sideration of  the  three-wire  system  for  electrolysis  mitigating 
purposes.  Recently,  however,  interest  in  this  system  has  been 
renewed,  and  at  least  some  of  the  difficulties  successfully  over- 
come, with  the  result  that  at  the  present  time  there  are  in 
operation  or  being  installed  two  sectionalized  three-wire  sys- 
tems— one  in  operation  in  the  Hollywood  district  of  Los  Angeles, 
Cal.,  and  the  other  in  process  of  installation  in  West  Springfield, 
Mass.  It  is  known  that  the  three-wire  system  has  been  in 
operation  for  some  twelve  years  in  Niirnberg,  Germany,  and 
for  a  considerable  length  of  time  in  Brisbane,  Australia. 

The  three-wire  system  may  take  two  different  forms,  which, 
though  the  same  in  principle,  differ  decidedly  as  to  the  arrange- 
ment of  the  feeders.  In  one  form,  known  as  the  Parallel  Three- 
wire  System,  one  trolley  of  a  double  track  road  is  negative  and  the 
other  positive,  the  tracks  being  neutral.  In  the  other  form,  known 
as  the  Sectionalized  Three-wire  System,  the  feeding  district  is  di- 
vided into  sections  and  alternate  sections  are  supplied  by  feeders 
running  directly  from  the  positive  bus,  while  the  remaining 
sections  are  supplied  by  feeders  from  the  negative  bus.  For 
a  more  detailed  description  of  these  two  forms  of  three-wire 
systems  reference  is  made  to  the  Bureau  of  Standards'  Tech- 
nologic Paper  No.  52. 

49.  Reversed  Polarity  of  Trolley  System.  With  the  ordinary 
construction  of  electric  railways  using  the  running  tracks  as 
a  part  of  the  electric  circuit,  the  overhead  trolley  wire  or  third 


AMERICAN   PRACTICE  57 

rail  is  made  the  positive  conductor,  and  the  running  tracks 
the  negative  or  return  conductor,  only  one  exception  to  this  rule 
being  known  to  the  Committee.  With  the  usual  arrangement 
stray  currents  escape  from  the  running  rails  into  ground  and 
flow  to  underground  structures  at  points  distant  from  the  power 
station,  and  such  escape  of  stray  currents  from  the  rails  gener- 
ally takes  place  from  a  large  area  of  outlying  lines.  The  cur- 
rent then  returns  to  the  tracks  from  ground  and  from  under- 
ground structures  in  the  neighborhood  of  the  power  station. 
For  this  reason  the  most  acute  danger  from  electrolysis  is 
usually  produced  on  underground  structures  in  the  neigh- 
borhood of  the  power  station. 

To  reverse  this  arrangement  of  polarity  and  make  the 
rails  the  positive  conductor,  causes  current  to  leave  the 
structures  over  widely  scattered  areas,  so  that  the  current 
density  leaving  the  underground  structures  will  be  so  small 
as  to  prevent  acute  danger  from  electrolysis.  This  arrange- 
ment is  being  used  in  New  Haven,  Conn,  at  the  present 
time.  It  is  found,  in  this  instance,  that  all  potentials  and 
currents  which  formerly  existed  when  the  rails  were  the  nega- 
tive conductor  have  now  reversed  in  direction,  but  have  the 
same  magnitude.  It  is  also  found  that  current  leaves  under- 
ground structures  over  a  widely  scattered  outlying  area.  This 
arrangement  has  not  been  in  operation  a  sufficiently  long  time 
to  determine  whether  or  not  the  danger  from  electrolysis  at 
any  one  outlying  point  will  become  acute.  The  reversal  of 
polarity  renders  extremely  difficult  the  effective  drainage  of  un- 
derground structures,  because  there  is  no  definite  point  of  mini- 
mum potential  to  which  to  drain. 

50.  Booster  System.  Negative  boosters  have,  in  the  past, 
been  employed  in  connection  with  drainage  systems,  and  are 
in  use  in  connection  with  the  insulated  track  feeder  system 
abroad,  but  not  in  this  country,  so  far  as  known.  The  use  of  nega- 
'tive  boosters  is  simply  a  means  of  caring  for  voltage  drop  other 
than  by  the  use  of  copper.  Boosters  have  proved  economical  under 
certain  conditions ,  and  uneconomical  under  others .  In  general  it  is 
simply  a  question  of  the  fixed  charges  on  copper  as  against  the 
fixed  charges  and  operating  cost  of  machines.  In  one  in- 
stance where  a  booster  was  employed  in  connection  with 
a  drainage  system  it  was  discontinued,  not  because  the 
addition  of  a  booster  to  a  drainage  system  was  unsatisfactory, 


58  AMERICAN   PRACTICE 

but  because  the  drainage  system  itself  did  not  adequately  care 
for  the  trouble.  Various  special  arrangements  involving  the 
use  of  boosters  in  electrolysis  mitigation  have  been  proposed, 
but  in  so  far  as  is  known  they  have  never  been  placed  in  suc- 
cessful operation. 

51.  Interconnection   of  Railway   Return    Circuits.      Where- 
ever  two  or  more  electric  railway  tracks  come  close  together, 
whether  they  belong  to  the  same  railway  system  or  to  different 
railway  systems,  large  differences  of  potential  between  them, 
with  resultant  high  potential  gradients  through  ground,  are  often 
found   to   occur   unless   the   tracks   are   electrically  connected. 
Interconnection  of  tracks    has    been    found    to    be    of   partic- 
ular advantage  where  two  or  more   lines   of   electric   railway, 
operating    in   one    locality   and  belonging   to   the  same   or  to 
different  systems,  are  supplied  from  two  or  more  power  stations 
located  in  different  parts  of  the  city.     By  interconnecting  the 
tracks  of  such  lines  in  the  neighborhood  of  the  power  stations, 
and   also    at    several   intermediate   points,    an   interchange   of 
current  has  been  brought  about,  whereby  the  .drop  formerly 
existing  in  one  track  has  been  balanced  by  the  drop  in  the 
opposite  direction  in  the  other  track,  the  rail  drop  in  each  track 
greatly  reduced,  and  all  high  potential  gradients  between  the 
tracks  eliminated.     This  reduction  in  rail  drop  resulted  also 
in  a  corresponding  reduction  of  losses. 

52.  Use  of  Alternating  Currents.     When  the  first  alternating 
current  railways  were  proposed,  the  question  of  possible  elec- 
trolytic   effects    received    special    investigation.     Considerable 
work  was  done  upon  a  laboratory  scale,  in  which  it  was  estab- 
lished that  alternating    currents    could    produce    corrosion    on 
electrodes   of  the  metals   commonly  used  underground,   such 
as  lead  and  iron,  but  that  the  effects  were  very  much  less  in 
magnitude  than  those  produced  by  equivalent   quantities  of 
direct  current,  usually  less  than  one  per  cent  and  in  most  cases 
negligible. 

It  has  not  as  yet  been  possible  to  determine  whether  these 
effects,  demonstrated  in  an  experimental  manner,  are  being 
reproduced  in  the  case  of  actual  installations.  In  the  case  of 
practically  all  actual  exposures  which  have  occurred  up  to 
the  present  time  it  has  been  impossible  to  dissociate  effects 
which  might  be  due  to  an  alternating  current  exposure  from 


AMERICAN   PRACTICE  59 

the  effects  which  are  due  to  a  simultaneous  exposure  to  stray 
currents  from  direct  current  railways.  Whether  alternating 
current  corrosion  is  proceeding  at  the  relatively  slow  rate  in- 
dicated by  the  experimental  investigations  and  will  at  some 
time  produce  damage  to  subsurface  structures,  cannot  now  be 
determined.  Special  measures  for  the  reduction  of  leakage  of 
current  to  earth  are  being  tried  out  in  one  alternating  current 
railway,  but  neither  the  construction  nor  the  results  have  yet 
been  made  public.  (See  Bureau  of  Standards  Technologic  Paper 
No.  72.) 

53.  Insulated  Track  Feeder  System.  The  insulated  track 
feeder  system  or  the  insulated  return  feeder  system  is  employed 
in  a  number  of  American  cities  at  the  present  time,  and  plans 
are  being  made  looking  to  its  installation  in  a  number  of  other 
cities. 

The  arrangement  of  feeders  described  under  this  title  is  not 
generally  understood,  and  as  it  is  commonly  confused  with  the 
reinforcement  of  track  conductivity,  the  following  explanation 
is  therefore  made. 

Stray  current  which  is  the  cause  of  electrolytic  corrosion  is 
traceable  directly  to  voltage  drop  in  the  rails.  With  a  given 
resistance  between  rails  and  earth  any  means  which  will  most 
effectively  reduce  this  voltage  drop  is,  therefore,  the  means 
which  will  most  effectively  reduce  electrolytic  corrosion.  The 
reinforcement  of  the  conductivity  of  the  rails  by  paralleling 
them  with  other  conductors  operates  definitely  in  this  direction, 
provided  the  paralleling  conductors  are  not  themselves  in  contact 
with  the  earth.  When,  however,  it  is  desired  to  reduce  the  volt- 
age drop  to  such  a  point  as  will  insure  reasonable  immunity  from 
electrolytic  troubles,  the  employment  of  copper  in  parallel  with 
the  rails  generally  proves  prohibitively  expensive.  For  example, 
an  average  grade  of  rail  has  a  resistance  12  J  times  that  of  copper 
of  the  same  cross-section.  Its  conductivity  is  therefore  ap- 
proximately the  equivalent  of  10,000  c.  m.  of  copper  per  pound 
per  yard.  Such  a  rail  weighing  100  pounds  per  yard  would  be 
approximately  equivalent  to  a  1, 000,000  c.  m.  cable.  To  reduce 
the  track  voltage  drop  to  one-half  its  former  value,  where  such 
a  rail  is  employed,  would  require  a  1,000,000  c.  m.  cable  laid 
parallel  to  each  rail  of  the  track  for  its  entire  length.  This  large 
investment  in  copper  would  reduce  the  losses  of  track  trans- 
mission by  but  one-half,  and  would  reduce  the  stray  current  by 


60  AMERICAN   PRACTICE 

one-half.  If  bare  copper  in  contact  with  the  earth  were  used 
the  stray  current  would  be  reduced  by  somewhat  less  than  one- 
half.  Thus,  the  practice  to  install  return  copper  to  reduce 
track  drop  with  a  grounded  bus-bar  is  either  prohibitively  ex- 
pensive or  ineffective.  It  was  because  of  these  recognized  diffi- 
culties that  the  Insulated  Track  Feeder  System  was  introduced. 

The  insulated  track  feeder  system  employed  in  the  Amer- 
ican cities  above  referred  to  has  the  following  distinguishing 
characteristics : 

(a)  The  negative  bus  is  insulated — that  is,  not  connected  to 
earth  nor  directly  to  the  rails  at  or  near  the  power  or  sub-station, 
except  that,  in  some  instances,  it  is  connected  to  the  rails  through 
resistances  sufficient  in  magnitude  to  insure  that  this  point  is  at 
approximately  the  same  potential  as  other  track  feeder  points. 

(b)  The  current  is  returned  to  the  negative  bus  by  insulated 
feeders  leading  from  selected  points  on  the  track  network. 

(c)  These  feeders  are  connected  to  the  track  at  their  extremi- 
ties only,  or,  if  connected  at  intermediate  points,  are  connected 
through  resistances  of  such  magnitude  as  to  keep  all  connected 
points  at  approximately  the  same  potential  with    respect  to  the 
bus. 

The  Insulated  Track  Feeder  System  is  thus  an  arrangement 
having  for  its  prime  object  the  reduction  of  stray  current  through 
the  earth.  The  insulated  feeders  are  installed  either  overhead 
or  in  underground  ducts,  and  extend  from  the  negative  bus  to 
such  points  on  the  track  network  as  have  been  determined,  by 
either  observation  or  computation,  to  be  those  from  which  the 
removal  of  current  will  prevent  excessive  track  voltage  drop. 
The  negative  bus  is  connected  to  the  rails  at  the  power  house 
only  through  a  resistance  sufficient  in  magnitude  to  insure  that 
this  point  is  at  approximately  the  same  potential  as  other  feeder 
connection  points.  When  all  feeder  connection  points  are  at 
the  same  potential  the  maximum  effectiveness  of  the  system  as  a 
means  of  reducing  stray  currents  is  found.  The  attainment  of 
this  condition  requires  track  bonding  of  a  reasonably  high  order 
of  uniformity. 

In  most  cases  feeder  connection  points  are  not  brought  to  the 
same  potential,  but  a  certain  drop  is  allowed  in  the  direction  of 
the  power  station. 

The  insulated  track  feeder  system  is  the  equivalent  of  having 
the  negative  bus-bar  of  the  power  supply  station  divided  into 
branches  corresponding  in  number  to  the  number  of  track  feeder 


AMERICAN   PRACTICE  61 

points,  and  distributed  geographically  over  a  considerable  por- 
tion of  the  track  network.  This  reduces  both  maximum  and 
average  current  in  the  rails  and  also  reverses  the  direction  of 
the  current  in  the  rails  on  one  side  of  each  feeder  point.  These 
changes  in  the  rail  current  directly  reduce  track  voltage  drop. 
The  area  from  which  current  leaks  to  earth  and  to  underground 
structures,  and  also  the  area  from  which  current  returns  from 
underground  structures  and  earth  to  the  rails  are  subdivided. 
The  combined  effect  of  these  factors  is  a  substantial  improve- 
ment in  electrolysis  conditions  of  underground  structures.  (See 
G.  I.  Rhodes,  Trans.  A.  I.  E.  E.,  1907.) 

The  efficacy  of  this  system  in  reducing  stray  current  is 
practically  independent  of  the  weight  of  copper  in  the  individual 
feeders — that  is  to  say,  the  voltage  drop  in  the  feeders  may  be 
either  large  or  small,  without  material  effect  upon  the  stray 
currents. 

As  was  pointed  out  under  a  prior  sub-heading,  negative  boosters 
may  be  used  with  this  system.  The  principles  underlying  the 
insulated  track  feeder  system  are  the  same,  whether  or  not 
negative  boosters  are  used. 

B.  MEASURES   APPLIED   TO   AFFECTED    STRUCTURES. 

54.  Insulating  Joints  in  Large  and  Small  Iron  Pipes  and  in  Lead- 
sheathed  Cables.  In  a  number  of  installations  flow  of  stray 
current  on  metallic  pipe  lines  has  been  prevented  by  the  use  of 
a  sufficient  number  of  insulating  joints.  It  is  found  that  where 
a  pipe  line  is  laid  with  every  joint  an  insulating  joint,  the  line 
has  such  a  high  electrical  resistance  that  no  measurable  current 
flows  on  the  line,  although  considerable  potential  gradient  exists 
in  earth  parallel  to  the  pipe  line.  In  some  installations  it  has 
been  found  sufficient  to  use  comparatively  few  insulating  joints 
to  break  up  the  electrical  continuity  of  a  pipe  line  and  protect  the 
line  from  electrolysis,  but  in  these  cases  it  was  necessary  to  make 
adequate  tests  to  assure  that  sufficient  current  did  not  shunt 
through  earth  around  the  joint  to  damage  the  pipe  on  the 
positive  side  of  the  joint.  In  these  installations  it  has  been  found 
necessary  to  install  such  insulating  joints,  not  only  in  the  positive 
areas,  but  also  in  the  negative  areas  in  all  places  where  con- 
siderable potential  gradient  in  earth  parallel  to  the  pipe  existed. 
It  is  found,  in  fact,  that  the  frequency  with  which  insulating 
joints  must  be  installed  in  a  pipe  line  in  order  to  assure  reasonable 
protection  from  electrolysis,  depends  upon  the  potential  gradient 


62  AMERICAN   PRACTICE 

'through  the  earth  and  upon  the  electrical  resistivity  of  the  earth 
in  the  neighborhood  of  the  pipe  line. 

Tests  on  joints  buried  in  earth  have  shown  that  the  resistance 
of  a  short  insulating  joint  is  practically  the  same  as  that  of  a 
long  joint,  but  that  a  long  insulating  joint  gives  a  more  even 
distribution  of  leakage  current  than  a  short  joint,  and  that, 
therefore,  a  long  insulating  joint  is  to  be  preferred  where  there  is 
considerable  potential  difference  across  the  joint  or  where  the 
resistivity  of  the  surrounding  soil  is  very  low.  It  has  also  been 
found  that  the  effect  of  a  long  joint  can  be  secured  from  a  short 
insulating  joint  by  surrounding  the  joint  and  the  pipe  for  some 
distance  on  each  side  of  the  joint  with  a  heavy  layer  of  insulating 
material.  In  a  number  of  installations  of  such  insulating  joints 
in  important  pipe  lines,  each  joint  and  the  pipe  for  a  distance 
of  from  5  to  25  feet  on  each  side  of  the  joint  have  been  surrounded 
by  a  wooden  box  leaving  a  space  of  from  1  to  2  inches  between  the 
outside  of  the  pipe  and  the  inside  of  the  box,  and  the  space  then 
rilled  with  pitch,  parolite,  or  similar  material.  In  this  way  an 
insulating  joint  having  an  effective  length  of  from  10  to  50  feet 
was  secured.  (See  also  Bureau  of  Standards  Technologic  Paper 
No.  52). 

In  a  large  number  of  cases  small  service  pipes  have  been 
damaged  by  electrolysis  from  stray  current  leaving  the  service 
pipes  for  earth,  which  current  was  found  to  flow  to  the  service 
pipes  either  from  the  main  or  from  house  piping.  In  the  latter 
case  the  current  was  found  to  reach  the  house  piping  by  way  of  a 
service  pipe  from  another  piping  system.  In  some  cases  of 
this  kind  such  current  flow  to  service  pipes  has  been  greatly  re- 
duced or  prevented  and  the  service  pipe  thereby  protected 
ffbm  electrolysis,  by  placing  an  insulating  joint  in  the  service 
pipe  at  the  main  or  in  the  building,  as  the  case  may  be. 

In  some  cases  it  was  however  found  necessary  to  install  an 
insulating  joint  in  the  service  at  the  main  and  a  second  joint 
in  the  building,  the  necessary  locations  of  the  joints  being 
determined  from  the  results  of  electrical  measurements.  This 
method  of  protecting  pipes  has  been  applied  to  isolated 
cases  which  were  specially  studied,  but  has  not  been  generally 
applied  to  a  large  complicated  city  system  of  mains  and  services. 

For  wrought-iron  or  steel  pipes  of  small  and  moderate 
size,  various  commercial,  insulating  joints  have  been  largely 
used.  For  large  sizes  of  pipe  a  flanged  type  of  insulating 
joint  has  been  commonly  used.  This  insulating  joint  has  been 


AMERICAN   PRACTICE  63 

made  up  by  placing  a  disc  of  insulating  material  between  the 
surfaces  of  the  flanges,  by  placing  insulating  tubes  over  the 
bolts,  and  by  placing  insulating  washers  under  the  bolt  heads 
and  nuts.  Red  fibre  has  been  most  commonly  used  for  the  in- 
sulating material,  except  that  for  water  pipes  in  some  cases  soft 
sheet  rubber  has  been  used  for  the  packing  between  the  flanges. 
Where  such  flanged  insulating  joints  have  been  used  in  cast-iron 
mains  the  flanges  have  generally  been  cast  as  part  of  the  pipe. 

For  water  mains  various  forms  of  insulating  joints  employing 
white  pine  wood  for  the  insulating  material  have  also  been  used 
to  a  considerable  extent.  For  cast-iron  water  mains  with  bell 
and  spigot  joints,  these  joints  have  in  some  installations  been 
rendered  insulating  by  placing  a  short  wooden  ring  between  the 
inside  of  the  bell  and  the  end  of  the  spigot  to  prevent  metallic 
contact  between  the  pipe  lengths,  and  then  calking  the  joint 
with  wooden  staves  of  clear  white  pine  shaped  to  fit  the 
curvature  of  the  pipe.  In  these  cases  the  spigot  end  of  the  pipe 
was  either  cast  without  a  bead  or  the  bead  was  removed.  The 
leaks  that  developed  in  the  joint  were  stopped  with  white  pine 
wedges.  These  simple  joints  have  been  found  satisfactory 
for  pressure  up  to  about  75  pounds  per  square  inch  (5.27  kg. 
per  sq.  cm.)  Where  with  higher  pressures  leakage  developed 
through  the  pores  of  the  wood,  this  was  overcome  by  dipping 
the  inner  ends  of  the  staves  in  red  lead.  The  staves  have  also 
been  reinforced  in  some  cases  by  an  iron  band  clamped  around 
the  spigot  end  of  the  pipe. 

It  is  found  that  cement  joints  in  cast  iron  pipes  as  ordinarily 
made  have  a  very  high  resistance  between  adjoining  lengths  of  pipe 
and  that  such  joints  may  properly  be  classed  as  insulating  joints. 
When  pipe  lines  are  laid  with  every  joint,  or  even  every  other 
joint  made  of  cement,  the  resistance  of  the  pipe  line  becomes  so 
great  that  the  current  flowing  on  the  pipes  will  be  greatly  re- 
duced. In  practice,  however,  for  mechanical  reasons  it  has  been 
found  that  cement  or  other  insulating  joints  cannot  be  used  under 
all  conditions  or  for  all  sizes  of  pipe.  In  such  cases,  the  entire 
drop  of  potential  of  the  pipe  line  is  distributed  more  or  less 
uniformly  over  all  of  the  cement  joints  and  the  drop  in 
potential  around  any  one  joint  is  too  small  to  cause  any  injury 
through  leakage  of  current  around  individual  joints  unless  the 
soil  is  of  great  conductivity. 

This,  however,  will  not  prevent  electrolytic  corrosion  in  local- 
ities where  current  can  reach  the  pipe  by  way  of  laterals,  or  when 


64  AMERICAN   PRACTICE 

it  is  closely  adjacent  to  other  conducting  structures  which  nul- 
lify the  effect  of  the  joints,  or  when  there  is  leakage  from  another 
transverse  pipe. 

Insulating  joints  in  lead  sheaths  of  underground  cables  are 
in  use  to  some  extent,  but  they  are  not  found  to  afford  an  effective 
primary  means  of  preventing  electrolysis.  In  some  installations 
such  insulating  joints  have  been  used  in  positive  areas  for  the 
purpose  of  breaking  up  the  electrical  continuity  of  the  lead  cable 
sheathing  and  stopping  rapid  localized  destruction  from  electro- 
lysis, but  such  joints  have  not  generally  been  found  to  afford 
permanent  and  complete  protection.  In  certain  special  cases 
in  practice  insulating  joints  have  been  used  in  the  lead  sheaths 
of  certain  cables  for  the  purpose  of  preventing  current  from  reach- 
ing the  remainder  of  a  cable  system.  Common  examples  of 
this  are  found  where  laterals  or  services  from  a  cable  system 
pick  up  considerable  current  from  an  iron  conduit  or  from  pipes 
with  which  the  cable  or  iron  conduit  may  be  in  accidental  metal- 
lic contact,  which  current  is  then  delivered  to  the  cable  system. 
Such  current  flow  to  the  cable  system  has  frequently  been  effec- 
tively stopped  by  introducing  an  insulating  joint  in  the  lead 
sheath  of  the  lateral  or  service  where  it  leaves  the  iron  conduit 
and  before  it  is  connected  to  the  main  cable  system. 

Particular  points  on  main  cable  runs  have  also  been  found 
where  considerable  current  was  picked  up.  Such  cases  have 
frequently  arisen  where  a  cable  crosses  a  bridge  in  an  iron 
conduit,  and  where  the  conduit  is  in  metallic  contact  through 
the  structure  of  the  bridge  with  trolley  tracks  on  the  bridge, 
whereby  large  currents  were  found  to  flow  from  the  tracks 
through  the  bridge  structure  and  iron  conduit  to  the  cable 
system.  In  such  cases  insulating  joints  have  been  installed 
on  each  side  of  such  sections  or  crossings  so  as  to  interrupt 
the  metallic  continuity  of  the  main  cable  sheath  and  prevent 
current  from  the  bridge  reaching  the  cable  system.  Where, 
after  this  was  done,  considerable  potential  differences  were 
found  to  exist  across  the  outer  ends  of  the  cable  sheaths,  these 
were  equalized  by  connecting  the  cable  sheaths  at  the  two  ends 
together  by  an  insulated  wire. 

A  simple  and  cheap  form  of  insulating  joint  for  lead  cable 
sheaths  which  has  been  very  generally  used  consists  in  cutting 
out  a  narrow  strip  of  lead  and  covering  the  break  with  a  suit- 
able insulating  and  waterproof  material  so  as  to  effectively 
prevent  entrance  of  moisture. 


AMERICAN   PRACTICE  65 

This  method  of  protecting  underground  structures  has  not 
been  widely  used  as  a  primary  means  of  electrolysis  protection, 
partly  because  of  the  great  expense  involved.  Further,  insulat- 
ing joints  unless  used  with  caution  may  introduce  serious  trouble 
at  many  points.  This  method  has  proved  useful  especially  in 
certain  new  installations,  but  to  protect  existing  installations 
by  this  means  would  involve  prohibitive  cost.  It  is  usually  re- 
garded as  a  suitable  auxiliary  measure  to  be  used  in  certain  cases 
which  cannot  economically  be  taken  care  of  by  other  means. 

55.    Insulating  Pipes,  Cables  and  Structural  Steel  from  Earth. 

Many  attempts  have  been  made  in  practice  to  protect  under- 
ground pipes  from  electrolysis  by  insulating  the  pipes  from 
earth  by  paints,  dips  or  insulating  coverings.  It  has  been 
found,  however,  that  no  dip  or  paint  will  permanently  protect 
a  pipe  from  electrolysis  in  wet  soil.  The  first  difficulty  that  is 
met  is  to  apply  the  paint  so  as  to  form  an  absolutely  perfect 
coating,  and  then  to  prevent  mechanical  damage  to  the  coating. 
Where  a  coated  pipe  is  in  a  positive  area  it  has  been  found  that 
aggravated  trouble  from  rapid  destruction  of  the  pipe  has 
resulted  at  spots  in  the  pipe  where  there  are  imperfections  in 
the  coating.  It  has  further  been  found  that  even  where  paints 
or  dips  are  apparently  intact,  electrolytic  action  has  taken 
place  causing  severe  pitting  under  apparently  good  coatings. 
It  has  been  found  that  in  most  cases  the  coatings  applied  have 
either  been  completely  destroyed  by  the  effects  of  the  wet 
soil  and  electric  currents,  or  defects  in  the  coating  have  de- 
veloped, causing  concentrated  corrosion  at  such  defective  spots.' 
It  has,  in  fact,  been  found-  that  pipes  located  in  positive  areas 
covered  with  imperfect  insulating  coatings  are  more  rapidly 
destroyed  by  electrolysis  than  bare  pipes  under  the  same  con- 
ditions. It  has  been  found  that  coating  pipes  in  negative  areas 
with  insulating  coverings  accomplishes  some  good  by  reducing 
the  amount  of  stray  current  which  reaches  the  pipe. 

Investigations  indicate  that  the  destruction  of  paints  in 
wet  soil  where  subjected  to  an  electric  current  is  probably  due 
to  a  trace  of  moisture  finding  its  w.ay  through  the  coating,  giv- 
ing rise  to  the  flow  of  a  feeble  current  and  resulting  in  a  very 
slight  amount  of  electrolysis.  The  gases  and  other  products 
of  electrolysis  then  form  blisters  and  finally  rupture  the  coating. 

Attempts  have  been  made  in  practice  to  apply  a  molten 
material  like  pitch  or  asphaltum  to  a  cold  pipe  in  the  field  by 


66  AMERICAN   PRACTICE 

means  of  brushes,  but  it  has  been  found  impossible  to  com- 
pletely cover  the  pipe  in  this  way.  A  type  of  insulating  cover- 
ing which  has  been  successfully  applied  in  a  number  of  installa- 
tions, and  which  appears  to  afford  certain  protection,  consists 
of  a  layer  of  at  least  from  1  to  2  inches  of  a  material  like  pitch 
or  parolite  of  such  a  grade  that  it  is  not  brittle  and  so  will  not. 
crack,  but  yet  is  hard  enough  to  remain  in  place.  It  has  been 
found  best  to  apply  such  a  layer  by  surrounding  the  pipe  with 
a  wooden  box,  supporting  the  pipe  upon  creosoted  blocks  of 
wood  or  upon  blocks  of  glass,  and  then  filling  the  space  between 
the  box  and  the  pipe  with  the  molten  material.  The  cost  of 
carrying  out  such  an  installation  is,  however,  large.  The 
method  has  been  applied  in  special  cases,  such  as  service  pipes 
in  very  bad  localities,  and  in  the  case  of  some  very  important 
individual  pipe  lines  of  comparatively  small  size. 

Attempts  have  been  made  to  protect  a  pipe  from  electrolysis 
by  imbedding  it  in  cement  or  concrete,  but  these  attempts 
have  not  been  successful,  even  where  the  cement  or  concrete 
was  several  inches  in  thickness.  The  reason  for  this  is  that 
concrete  in  damp  earth  acts  as  an  electrolytic  conductor,  like 
damp  soil,  and  therefore  cannot  afford  protection  from  elec- 
trolysis. 

The  following  experience  and  practice  is  that  of  a  gas  com- 
pany in  a  large  city  which  uses  cast-iron  pipes  in  general  in  their 
distributing  system  with  wrought -iron  services.  They  make 
it  a  uniform  practice  to  protect  all  of  their  service  pipes  with  an 
insulating  coating.  As  a  preliminary  the  pipes  are  first  cleaned 
with  a  wire  brush,  in  order  to  remove  all  scale.  They  are  then 
dipped  into  a  hot  coal  tar  compound,  then  wrapped  for  the 
entire  length  with  a  strip  of  canvas,  and  then  again  dipped  in 
the  compound.  In  spite  of  this  protection,  however,  they  have 
some  trouble  with  their  services.  The  difficulty  is  due  to  their 
inability  to  get  a  continuous  coating  over  the  entire  surface 
of  the  pipe.  Small  pin  holes  are  left  in  the  coating  due  to  minute 
bubbles  of  air,  or  some  similar  cause,  so  that  if  the  pipes  are 
positive  the  flow  of  current  from  the  pipe  through  moist  earth 
is  confined  to  these  minute  pin  holes  through  the  insulating 
compound.  The  result  is  that  the  action  of  the  current  forms 
a  small  blister  of  iron  rust  at  the  point  where  the  pin  hole  is 
located,  and  after  the  blister  becomes  so  large  as  to  loosen  a 
piece  of  the  compound,  the  action  takes  place  at  a  very  rapid 
rate  and  soon  destroys  the  pipe.  In  some  locations  some  of  the 


AMERICAN   PRACTI-CE  67 

service  pipes  have  to  be  renewed  within  a  period  of  six  months 
on  account  of  the  leaks  caused  by  the  electrolytic  corrosion. 

Attempts  have  been  made  to  insulate  lead-sheathed  cables 
from  earth,  but  these  attempts  have  not  generally  been  at- 
tended with  beneficial  results.  The  experience  of  the  telephone 
companies,  who  are  the  largest  users  of  lea-d-sheathed  cables, 
has  been  that  it  is  futile  to  attempt  to  insulate  lead-sheathed 
cables  from  earth.  It  is,  however,  the  practice  of  the  telephone 
companies  to  make  every  effort  to  prevent  metallic  contact 
between  their  lead-sheathed  cables  and  other  grounded  struc- 
tures throughout  the  run  of  the  cable,  except  where  it  has  been 
determined  by  a  careful  survey  that  a  drainage  connection  to 
some  particular  structure  is  required  for  the  protection  of  the 
cable. 

The  use  of  insulating  ducts  has  been  proposed  at  various 
times,  but  investigations  of  the  telephone  companies  do  not 
show  that  their  use  affords  satisfactory  insulation  of  the  cable 
sheaths  from  earth,  with  the  result  that  the  telephone  com- 
panies do  not  place  any  reliance  in  any  insulating  property 
that  any  of  the  duct  material  may  inherently  possess.  The 
principal  duct  material  at  present  used  by  the  telephone  com- 
panies for  main  cable  subway  runs  is  vitrified  clay  and  creo- 
soted  wood.  For  laterals  and  short  cable  runs  iron  pipe  is 
frequently  used. 

Laying  telephone  cables  in  troughs  and  surrounding  them 
solidly  with  asphalt  was  a  method  employed  in  the  early  days 
of  telephone  construction,  but  this  method  was  abandoned 
because  of  its  inflexibility  and  because  of  the  great  difficulty 
of  repairing  defects  or  replacing  cables.  It  was  further  found 
that  this  method  did  not  positively  insulate  the  cables  every- 
where from  earth  on  account  of  cracks  and  other  discontinuities 
in  the  asphalt  which  were  found  in  practice  to  develop. 

Steel  tape  armored  cables  protected  with  a  thoroughly 
saturated  jute  covering  have  been  used  buried  directly  in  earth. 
Such  covering  has  been  found  to  be  effective  for  a  number  of 
years  in  protecting  the  armor  against  electrolytic  corrosion, 
except  at  points  where  the  jute  has  been  abraded  or  cut  so 
as  to  expose  the  metal. 

Where  steel  structures  extending  underground  are  located 
so  as  to  be  subjected  to  electrolytic  action,  the  portions  below 
ground  have  been  enclosed  with  insulating  materials.  For  this 
purpose  any  material  that  excludes  water,  as  for  instance 


68  AMERICAN   PRACTICE 

paints  having  an  asphalt  base,  have  been  successfully  used, 
while  many  of  the  ordinary  paints  have  not  been  found  effective. 
It  has  also  been  found  that  surrounding  steel  with  concrete 
where  this  is  imbedded  in  damp  earth  does  not  afford  absolute 
protection  against  electrolysis,  although  the  electrolytic  action 
is  most  severe  at  first  and  becomes  less  with  time,  because  the 
formation  of  chalk  in  the  concrete  fills  the  pores  of  the  concrete 
and  increases  its  resistance  and  the  iron  oxide  forming  on  the 
surface  of  the  metal  also  increases  the  resistance.  Special 
preparations  of  Portland  cement  properly  applied  so  as  to  be 
watertight  have  also  been  found  to  afford  good  protection. 

56.  Shielding,  or  the  Use  of  an  Auxiliary  Anode.  In  some 
special  cases  underground  structures  have  been  protected  from 
electrolysis  by  connecting  to  the  structure  an  auxiliary  metallic 
conductor  located  so  as  to  cause  the  current  to  flow  to  earth 
from  the  auxiliary  conductor.  This  mode  of  protection  is 
known  as  shielding.  When  applying  this  method  it  has  been 
found  necessary  to  take  care  that  the  auxiliary  shielding  con- 
ductor does  not  merely  increase  the  electrode  areas  from  which 
the  current  leaves,  because  in  this  case  the  current  will  continue 
to  leave  from  the  structure  which  is  to  be  protected.  This 
has  been  found  to  be  the  practical  result  where  a  shielding 
conductor  of  the  same  or  less  contact  area  was  placed  in  earth 
near  the  structure  to  be  protected  and  where  the  stray  current 
then  left  from  both  structures.  The  shielding  conductor  must 
be  so  placed  that  current  will  be  prevented  from  leaving 
the  structure  to  be  protected  or  so  as  to  cause  its  magnitude 
to  be  greatly  reduced.  The  method  has  in  some  installations 
been  applied  to  a  structure  which  forms  the  dead  end  of  an 
underground  metallic  system  and  where  the  structure  is  highly 
positive  to  earth.  In  cases  of  this  kind  it  has  been  found  that 
the  current  leaves  at  relatively  high  density  from  and  near  the 
dead  end  of  the  structure,  with  the  result  of  rapid  destruction 
of  the  portion  near  its  dead  end.  In  such  cases  an  auxiliary 
shielding  conductor  of  adequate  contact  surface  extending  be- 
yond the  dead  end  and  electrically  connected  to  the  structure 
to  be  protected  has  been  installed  in  such  a  manner  that  the 
bulk  of  the  current  was  caused  to  leave  the  auxiliary  shielding 
conductor,  thus  affording  a  certain  degree  of  protection  to  the 
dead  end  of  the  structure. 

The  shielding  method  has  also  been  effectively  applied  for 


AMERICAN   PRACTICE  69 

the  protection  of  relatively  small  iron  or  steel  pipes,  such  as 
service  pipes.  In  these  cases  the  service  pipe  has  been  sur- 
rounded by  a  larger  metal  pipe  electrically  connected  to  the 
smaller  pipe.  One  application  of  this  method  which  is  in  use 
is  that  of  a  service  pipe  crossing  under  tracks  or  crossing  other 
structures  to  which  it  is  positive  and  where  the  pipe  comes 
relatively  close  to  the  rails  or  other  structures  at  the  point  of 
crossing.  In  these  cases  a  larger  shielding  pipe,  usually  of 
heavy  cast  iron,  has  been  placed  around  the  service  pipe  and 
electrically  connected  to  the  service  pipe  and  extended  suf- 
ficiently on  each  side  of  the  crossing  so  that  the  major  part  of 
the  current  was  caused  to  leave  the  shielding  pipe,  thereby 
corroding  the  shielding  pipe  while  protecting  the  service  pipe. 

57.  Drainage  of  Earthed  Metallic  Structures. 

(a)  Lead-sheathed  Telephone  and  Power  Cables.  The  method 
of  protection  against  electrolysis  used  generally  by  telephone 
companies  for  their  cable  sheaths  consists  of  installing  insulated 
conductors,  called  drainage  wires,  between  the  negative  re- 
turn system  of  the  railway  and  points  on  the  cable  system 
where  the  positive  potential  to  earth  is  highest.  The  purpose 
of  these  drainage  wires  is  to  conduct  the  stray  railway  current 
from  the  cable  sheaths  to  the  railway  negative  return  circuit, 
thereby  preventing  this  current  from  flowing  from  the  cable 
sheaths  to  earth  and  causing  corrosion  from  electrolysis.  In 
order  to  afford  complete  protection  it  has  been  found  that  such 
drainage  wires  must  have  sufficient  conductivity  and  must  be 
so  located  that  the  lead  sheath  of  the  cable  network  is  every- 
where lower  in  potential  than  the  adjacent  earth. 

As  the  potential  of  the  cable  sheath  is  lowered  by  the  con- 
nection of  the  drainage  wire  from  the  railway  negative  return 
circuit  the  current  flowing  on  the  cable  sheath  is  thereby  in- 
creased. In  order  that  this  current  does  not  become  excessive, 
care  is  taken  to  prevent  contacts  between  cable  sheaths  and  other 
underground  structures,  through  which  currents  could  flow 
to  the  cable  sheaths. 

The  drainage  method  is  also  employed  to  a  considerable 
extent  for  the  protection  of  underground  power  cables,  and  the 
principles  involved  in  its  application  are  the  same  as  for  tele- 
phone cables.  When  power  cables  are  worked  at  relatively 
high  temperatures  they  should  not  also  carry  a  heavy  drainage 
current  which  might  cause  over  heating.  Where  such  conditions 


70  AMERICAN   PRACTICE 

prevail  drainage  is  not  employed,  but  insulating  joints  are  used 
to  break  up  the  continuity  of  the  lead  sheaths. 

(b)  Pipe  Systems:  The  early  success  of  the  drainage  method 
in  affording  protection  against  electrolysis  of  lead-sheathed 
cables  led  to  the  proposal  to  apply  the  same  method  of  protection 
to  underground  piping  systems.  The  result  has  been  that 
in  some  cases  drainage  has  been  applied  to  gas  and  water  piping 
systems  to  a  greater  or  lesser  extent.  Some  of  these  installations 
are  reported  to  be  a  success,  while  others  are  reported  to  have 
been  attended  with  objectionable  results. 

It  has  been  found  that  there  are  certain  differences  between 
the  application  of  drainage  to  pipes  and  the  application  of  drain- 
age to  cable  sheaths.  The  principal  difference  that  has  been 
found  is  that  the  cable  sheaths  are  electrically  continuous  and 
uniform  conductors,  while  the  pipes  are  generally  non-uniform 
and  sometimes  discontinuous  conductors,  by  reason  of  the  joints. 
It  is  found  that  where  current  flows  along  a  pipe  and  encounters 
a  high  resistance  joint,  part  of  the  current  will  leave  the  pipe  on 
the  positive  side  of  the  joint  to  flow  to  some  other  underground 
conductor  or  to  shunt  around  the  joint  and  thereby  cause  electro- 
lytic corrosion  of  the  pipe  on  the  positive  side  of  the  joint. 

Another  difference  between  lead -sheathed  cables  and  piping 
systems  is  that  the  cables  are  relatively  small  and  are  con- 
tained in  ducts,  so  that  unless  they  are  submerged  they  are 
not  in  direct  contact  with  earth,  except  at  infrequent  points, 
whereas  gas  and  water  pipes  form  extensive  systems  and 
are  buried  directly  in  earth.  It  is  found  as  a  result  of  this  that 
a  drainage  connection  from  an  underground  piping  system 
generally  causes  very  much  larger  currents  to  flow  on  the  piping 
system  than  a  drainage  connection  from  an  underground  cable 
system. 

In  the  application  of  the  drainage  system  it  has  been  found 
that  unless  all  sub-surface  metallic  structures  affected  by  stray 
currents  have  been  bonded  together  in  such  a  way  that  at  every 
point  where  the  different  structures  come  into  proximity  to  one 
anotherall  are  maintained  at  the  same  potential,  damage  to  the  un- 
connected structures  has  in  certain  instances  resulted  from  a  flow 
of  current  through  earth  from  the  structure  of  higher  to  that  of 
lower  potential,  thus  causing  electrolysis  of  the  former.  As  struc- 
tures owned  by  different  interests  cannot  be  bonded  together  ex- 
cept by  an  agreement  between  the  owners,  this  has  frequently  of 


AMERICAN   PRACTICE  71 

itself  made  it  impossible  to  apply  a  comprehensive  drainage  sys- 
tem to  all  structures,  because  of  the  impossibility  of  obtaining 
an  agreement  of  all  owners  to  allow  connections  to  their  struc- 
tures, except  on  condition  that  another  interest  assume  liability 
for  any  injury  which  may  result  from  such  connections. 

Current  flowing  on  piping  systems  which  convey  inflammable 
substances  such  as  gas  or  oil  constitutes  a  danger,  as  cases 
have  been  reported  where  stray  currents  on  pipes  have  caused 
arcs  which  have  ignited  the  gas  or  oil  when  an  intentional  or 
accidental  break  in  the  pipe  has  occurred.  In  other  instances 
serious  damage  from  explosions  and  fire  has  been  caused  by 
an  arc  due  to  the  intermittent  contact  between  pipes. 

(c.)  Structural  Steel.  In  a  .number  of  installations  special 
precautions  have  been  taken  to  prevent  stray  current  from  reach- 
ing structural  steel.  Where  in  these  cases  such  currents  were 
found  to  reach  the  structure  by  means  of  pipes  or  other  metallic 
connections,  insulating  joints  have  been  placed  in  such  connec- 
tions, or  these  pipes  or  conductors  have  been  carried  on  insulated 
supports.  In  some  cases  where  flow  of  stray  currents  to  a  steel 
structure  could  not  be  entirely  prevented,  drainage  connections 
from  the  structure  to  the  railway  negative  return  circuit  have 
been  installed  to  remove  the  stray  current  from  the  structure, 
and  where  there  were  expansion  joints  in  the  structure  these 
have  been  bonded  across  by  metallic  conductors. 

C.  PATENTED  PROTECTIVE  SYSTEMS. 

58.  Foreign  and  Domestic  Patents.     There  have  been  many 
patents  taken  out  in  this  country  and  abroad  within  the  last 
twenty    years,    covering    systems    of    electrolysis    mitigation. 
Reference  may  be  had  to  Technologic  Paper  No.  52  issued  by 
the  Bureau  of  Standards,  Washington,  D.  C. 

D.     ORDINANCES   AND   DECISIONS. 

59.  Ordinances.    A  number  of  cities  have  ordinances  directed 
to  the  construction  and  operation    of   electric  railways.     The 
Committee,    however,    does    not    possess  .  sufficiently   definite 
information  as  to  the  extent  to  which  they  have  been  put  into 
effect   or  the  results  secured  to  warrant  it  in  stating  any  facts 
regarding  them  at  present. 


72  AMERICAN   PRACTICE 

60.  Decisions  of  Courts.  While  there  have  been  several  cases 
of  electrolysis  litigation  in  this  country  each  of  these  has  either 
been  concerned  only  with  certain  phases  of  the  subject  or  has 
been  limited  by  local  conditions,  so  that  there  are  no -leading 
decisions  by  courts  in  this  country  which  define  specifically 
the  duties  and  rights  of  the  several  parties  concerned'. 


EUROPEAN   PRACTICE  73 


IV.  EUROPEAN  PRACTICE. 

A.  GENERAL. 

61.  Personal  Investigation  Necessary.     In  the  study  of  the 
practice  followed  in  European  countries  in  handling  the  problem 
of  electrolysis,    it  appeared  impossible  to  secure  reliable  and 
satisfactory  information  by  mere  correspondence  and  consulta- 
tion of  published  reports  and  regulations ;  and  further,  since  the 
important  independent  investigations  made  by  American  in- 
vestigators several  years  ago  were  private  and  made  from  the 
standpoint  of  some  special  industry  rather  than  from  a  com- 
prehensive   all-around  point  of  view  the  necessity  of  an    in- 
dependent investigation  was  made  evident. 

The  Chairman  of  this  Sub-Committee,  after  consultation 
with  its  members  and  the  General  Chairman  decided  to  visit 
several  important  European  countries  during  the  summer  of 
1914.  He  was  accompanied  by  Mr.  A.  Maxwell,  Testing 
Officer  of  The  New  York  Edison  Company,  who  was  thoroughly 
conversant  with  electrolysis  measurements  and  surveys.  The 
effort  to  have  the  Bureau  of  Standards  appoint  a  representative 
to  join  the  visiting  representatives  failed  on '  account  of  ex- 
tensive engagements  of  the  Bureau,  but  a  consultation  was  held 
in  Washington,  and  the  field  of  inquiry  and  special  points  to 
be  looked  after  were  carefully  discussed,  and  a  list  of  classified 
questions  prepared,  so  that  as  far  as  possible  uniformity  of 
system  of  investigation  could  be  followed  in  all  instances. 
Similar  consultations  were  held  with  members  of  the  main 
Committee.  Information  on  important  foreign  cities  and 
authorities,  was  'received  from  Mr.  H.  S.  Warren,  also  foreign 
papers,  suggestions  and  references  from  Prof.  Albert  F.  Ganz. 

62.  Countries  Visited.     The  visiting  Committee  spent  June 
and  July  in  its  investigation,  covering  Germany,  Italy,  France 
and  England.     In  each  country  an  effort  was  made   to    take 
measurements  and  collect  data  and  surveys,  also  to  interview 
the  most   prominent   people  in   each  branch   of   the  different 


74  EUROPEAN   PRACTICE 

interests  affected  by  the  problem  of  electrolysis;  in  each  case 
extended  and  often  repeated  conferences  were  held  with  the 
engineers  most  familiar  with  the  details,  either  in  their  capacity 
of  specialized  consulting  engineers  or  officials  of  corporations 
or  public  authorities  directly  concerned  in  the  surveys,  disputes, 
administrative  measures,  etc.  relating  to  electrolysis. 

The  essential  and  characteristic  results  of  the  investigation 
are  briefly  outlined  in  the  following  paragraphs,  classified  by 
countries  visited.  The  references  and  appendixes  to  this  sum- 
mary should  be  consulted  for  details  of  design,  operation  and 
statistical  information. 

B.     GERMANY. 

63.  Laws  and  Ordinances.  There  are  no  specific  statu- 
tory laws.  The  common  law  of  most  States  prescribes 
that  all  the  conditions  under  which  a  corporation  is  to 
operate  must  be  prescribed  in  the  original  grant  or  for  any 
extension  of  lines,  and  the  law  prescribes  that  due  publicity 
be  given  to  any  request  for  a  franchise  or  extension  of  lines, 
so  as  to  enable  all  parties  which  may  be  affected  to  place  on 
record  any  limitation,  or  possible  damage  they  wish  to  be  pro- 
tected against,  before  the  concession  is  granted  to  the  applicant. 
Hence,  a  pipe  owning  company  organized  subsequently  to 
the  existence  of  an  electric  railway,  could  not  claim  damages 
for  electrolysis  from  this  electric  railway  unless  the  original 
franchise  to  the -railway  contained  a  clause  regarding  electrol- 
ysis damages  from  stray  currents. 

On  the  other  hand,  when  the  municipality  undertakes  the 
construction  and  operation  of  a  tramway  system,  the  pipe 
owning  companies  then  in  existence  are  deprived  of  the  privilege 
of  demanding  that  protection  against  possible  future  damages 
by  electrolysis  which  would  be  accorded  to  them  in  the  case  of 
a  new  private  railway  company.  The  municipality  does  not 
assume  legally  the  obligation  to  protect  the  existing  interests 
against  possible  damages  by  electrolysis.  The  municipalities, 
however,  both  for  their  new  railway  constructions,  as  well  as 
for  new  extensions  of  existing  companies'  railways,  always 
prescribe  that  they  be  constructed  and  operated  in  accord- 
ance with  existing  technical  standards. 

The  recommendations  of  the  German  Earth  Current  Com- 
mission are  recognized  as  the  existing  technical  standards  re- 


EUROPEAN   PRACTICE  75 

garding  matters  relating  to    electrolysis,    and  in   this  manner 
they  have  assumed  almost  the  importance  of  law. 

64.  Commission  Recommendations.    The  German  Earth  Cur- 
rent Commission's  recommendations   adopted  in   1910   by  the 
German  Electrotechnical  Society  prescribe  the  following: 

In  large  cities,  the  maximum  rail  drop  is  to  be  limited,  in  the 
urban  net-work  and  for  a  distance  of  2  km.  beyond,  to  2.5  volts 
and  to  1  volt  per  km.  beyond  this  central  district.  Exceptions 
are  made  for  roads  operating  only  a  few  hours  a  day.  (It  may 
be  noted  here  that  the  maximum  drop  is  interpreted  to  be 
the  average  maximum  drop  for  the  period  of  the  normal  day 
traffic,  usually  18  hours  in  every  24  hours.)  Bonds  must  not 
increase  the  resistance  of  tracks  over  20% — must  be  tested 
yearly  and  when  a  connection  shows  a  resistance  higher  than 
10  meters  of  rail  it  must  be  repaired.  Connections  to  pipes 
are  prohibited.  Bare  feeder  returns  are  not  allowed.  Pilot 
wires  are  prescribed. 

Since  these  regulations  were  promulgated  from  20  to  30 
installations  in  Germany  (some  municipally  owned  and  some 
privately)  have  taken  steps  to  bring  up  their  standard  of  con- 
struction to  meet  these  regulations. 

65.  Construction.     In  large  cities,  like  Berlin,  the  railways 
are 'supplied  by  a  great  number  of  combination  light  and  rail- 
way  substations  feeding  limited   districts,   entailing  relatively 
small  positive  line  drops  of  potential.     In  some  cases  like  Berlin, 
each  feeding  point  is  fed  by  positive  and  negative  cables  of 
equal   cross-section. 

Insulated  returns  with  balancing  resistances  are  predom- 
inantly used  in  Germany,  though  there  are  a  few  installations 
with  negative  boosters,  like  Danzig,  where,  however,  insulated 
returns  with  balancing  resistances  as  well  as  boosters  are  used. 

There  are  very  few  large  installations  using  bare  returns. 
The  "drainage  system"  was  used  in  Aachen  but  it  is  now  a 
subject  of  litigation. 

66  Conditions.  In  general  the  electrolysis  conditions  through- 
out Germany  are  now  very  satisfactory.  In  the  past  the  majority 
of  troubles  have  been  on  gas  and  water  pipes,  or  at  least  these 
have  received  more  attention  in  the  reports.  The  railway 
experts  expressed  the  opinion  that  the  regulations  were  too 


76  EUROPEAN   PRACTICE 

stringent;  the  gas  and  water  pipe  experts  expressed  the  opinion 
that  the  regulations  were  too  lenient.  The  studies  are  made 
in  the  most  excellent,  technical  manner  and  the  conclusions 
arrived  at  appear  to  be  practicable*  and  reasonably  acceptable 
to  all  parties  concerned. 

Measurements  were  made  by  the  Sub-Committee  of  one  large 
installation  and  it  was  found  that  the  maximum  drops  in  rails 
were  well  within  the  limits  prescribed  by  the  German  regulations. 
More  extended  measurements  were  omitted,  depending  for 
other  information  on  the  surveys  made  by  the  German  Earth 
Current  Commission. 

C.     ITALY. 

67.  Laws  and   Ordinances.     The   Government   has   not   en- 
acted any  law  affecting  the  operation  of  electric  railways  in 
relation  to  electrolysis    problems,    nor    has    any  municipality 
issued  regulations  on  the  subject. 

68.  Construction.     Bare  returns  are  generally  used,  in  large 
installations. 

69.  Conditions.     From  a  survey  made  in  a  city  six  years 
ago,  it  was  found  that  the  maximum  differences  of  rail  potential 
were  as  great  as  17.5  volts  between  station  and  distant  points 
about   three   miles   away.     In   this   installation   they   had   not 
received  complaints  of  serious  damages  by  electrolysis,  except 
a  few  gas  service  pipes,  though  the  railroad  itself  had  experi- 
enced some  difficulties  on  water  pipes  at  one  of  its  yards. 

Some  of  the  larger  systems  in  important  cities  are  alive  to 
the  situation  and  are  following  with  interest  the  developments 
in  other  countries. 

In  general,  troubles  from  electrolysis  have  been  considered  in- 
significant in  the  Italian  practice. 

D.     FRANCE. 

70.  Laws  and  Ordinances.     A  Ministerial  Decree  of  March 
21,    1911,   prescribes  that  the  maximum  voltage  drop  in  rail 
returns  of  electric  tramways  shall  not  exceed  one  volt  per  kilo- 
meter, except  in  locations  where  there  do    not    exist    metallic 
masses   in   the   neighborhood   of   the   tracks,    where   the   limit 


EUROPEAN   PRACTICE  77 

may  be  exceeded.  No  definition  is  given  of  the  time  element 
in  the  measurement  of  the  maximum  drop,  'except  by  stating 
that  it  must  be  the  average  during  the  normal  passage  of  the 
cars.  The  same  decree  prescribes  that  the  bonds  must  be 
kept  in  the  best  possible  condition,  that  the  resistance  of  each 
must  not  be  greater  than  10  metres  of  normal  rail  and  that 
periodic  tests  must  be  made  and  recorded  on  a  register  which 
must  be  subject  to  inspection  on  the  call  of  the  control  service. 
The  return  feeders  must  be  insulated. 

71.  Construction.     While  the  Government  regulations  pres- 
cribe the  use  of  insulated  returns,  we  were  informed  that  in 
general  the  practice  is  to  connect  the  rails  to  the  negative  bus 
and  to  rarely  use  insulated  returns.     Noticeable  exceptions  are 
the  Paris  conduit  system  tramways  using  complete    insulated 
returns,  and  the  Paris  Nord-Sud  Subway  Company  operating 
a  three  wire  system  with  the  rails  as  neutral. 

72.  Conditions.     The    investigation    was    somewhat    limited 
in  France.     In  general  serious  electrolysis  troubles  were  found 
only  in  a  few  situations,  either  created  by  installations  of  heavy 
traffic  electric  lines,  or  by  peculiar  conditions  not  readily  ex- 
plainable.    The  maximum  drop  of  potential  between  pipe  and 
rail  measured  by  this  Committee  was  about  6  volts  at  a  loca- 
tion where  trouble  has  been  persistent  and  serious. 

Damage  has  been  caused  in  the  past  to  gas  pipes  in  Paris 
during  the  period  of  transformation  of  the  old  two-wire,  three- 
wire  and  five- wire  systems  of  electric  light  distribution,  but 
all  of  these  troubles  were  only  of  temporary  character  and 
were  promptly  remedied  as  soon  as  discovered. 

Many  suits  (about  twenty)  for  electrolysis  damages  are  being 
tried  in  Paris.  On  account  of  the  situation  created  by  these 
suits  the  Paris  municipality  and  the  government  have  recently 
appointed  a  Commission  to  investigate  the  subject  and  make 
recommendations  regarding  the  electrolysis  situation  in  the  City 
of  Paris. 

0 

E.     ENGLAND. 

73.  Laws  and  Ordinances.     The  Board  of  Trade  regulations 
prescribe  that  the  maximum  rail  drop  shall  not  exceed  seven 
volts.    In  practice  the  Board  takes  as  the  voltage  drop  the  mean 


78  EUROPEAN   PRACTICE 

between  the  average  and  the  momentary  maximum  values  for 
the  period  of  a  schedule  run  at  time  of  maximum  traffic,  exclu- 
sive of  exceptional  occasions  like  athletic  games,  etc.  The  per- 
iods assumed  vary  from  15  to  30  minutes.  The  regula- 
tions also  contain  other  requirements,  prescribing  measure- 
ments of  track  leakage,  etc.;  in  actual  practice,  however,  little 
attention  is  paid  to  any  other  requirements  as  long  as  the 
seven  volt  over-all  rail  drop  is  not  exceeded. 

74.  Construction.      Whenever    the     resistance    of  the  rails 
would  give  a  drop  in  excess  of  seven  volts,  insulated  return 
feeders    with    resistances,  or  negative  boosters    are    used;    the 
latter  more  extensively  than  in  any  other  country. 

75.  Conditions.     The  sub-committee  found  that  in  all   the 
several  cities  visited  the  Board  of  Trade  regulations  were  met 
well  within  the  limits.     In  fact,  on  the  average  the  maximum 
drops  measured  in  all  large  cities  visited  in  the  months  of  Ju*ie 
and  July  were  about  two  volts. 

The  Board  of  Trade  regulations  are  not  considered  onerous 
by  any  of  the  railway  engineers  we  consulted.  All  authorities 
representing  the  pipe  owning  companies,  the  railways,  the 
State  telegraph  and  telephone  and  the  Board  of  Trade  were 
unanimous  in  stating  that  the  electrolysis  situation  on  the 
properties  under  their  respective  control  was  entirely  satis- 
factory. 

The  only  question  raised,  and  this  only  by  a  limited  number 
of  pipe  owning  entities,  is  whether  the  electric  railways  should 
not  be  held  legally  responsible  for  any  damages,  even  when 
they  comply  with  the  Board  of  Trade  regulations.  Two  or 
three  attempts  have  been  made  to  have  a  law  passed  by  the 
Parliament  to  this  effect,  and  two  or  three  pipe  exhibits  have 
been  repeatedly  presented  to  prove  electrolysis  damages,  but 
the  Parliament  refused  to  act. 

The  seven  volt  limitation  is  considered  somewhat  of  a  hap- 
hazard empirical  measure  formulated  many  years  ago,  but 
having  given  good  results  it  is*  considered  good  enough,  though 
it  is  conceded  that  some  more  rational  measure  could  probably 
now  be  devised  to  replace  it.  However,  no  demand  was  dis- 
covered for  a  change  on  the  part  of  anyone  concerned. 


EUROPEAN   PRACTICE  79 

F.     SUMMARY  AND  CONCLUSIONS. 

76.  Germany  through  voluntary  co-operation  has  probably 
remedied   the   former  dangerous   electrolysis   conditions   in   all 
of  its  important  systems.     The  instrumentality  of  agreements 
on   definite   technical   standards   was   sought   in   preference   to 
legislation  for  different  states. 

Italy  will  probably  give  more  consideration  to  the  subject 
of  electrolysis  whenever  the  general  conditions  will  permit. 

France  has  not  been  as  successful  in  bringing  prompt  results 
through  legislation,  as  has  Germany  through  technical  co- 
operation. 

England,  which  has  had  the  benefit  of  Government  regula- 
tion for  many  years,  has  now  no  electrolysis  troubles  nor  dis- 
putes. 

In  Germany  and  England,  the  subject  of  electrolysis  has 
received  extensive  study  and  consideration.  The  attached 
typical  abstracts  of  reports  of  the  German  Earth  Current 
Commission  and  the  appendix  of  the  detail  report  of  the  Sub- 
Committee  are  evidence  of  the  methods  followed  and  the  satis- 
factory results  obtained  abroad  by  adopting  the  following 
measures : 

1st.     Maintenance  of  good  bonding. 

2nd.  Elimination  of  intentional  contacts,  and  liberal  separ- 
ation, whenever  possible,  of  pipes  and  rails. 

3rd.  Avoidance  of  bare  copper  returns  and  use  of  insulated 
returns  in  all  installations  where  the  conductivity  of  the  rail 
alone  would  give  a  too  great  maximum  rail  drop. 

4th.  Use  of  insulated  returns  with  balancing  resistances, 
or  to  a  lesser  extent  "boosters,"  for  the  purpose  of  maintaining 
equality  of  rail  potential  at  the  feeding  points  of  all  feeders. 

5th.  Small  feeder  drops  and  frequent  substations  to"  give 
close  line  regulation. 

77.  Application  to  American  Conditions.     This  study  has  not 
been  made  with  the  object  of  arriving  at  definite  recommenda- 
tions, but  to  point  out  that  disputes  on  account  of  electrolysis 
troubles  have  been  prevalent  in  the  past  in  all  countries  before  sys- 
tematic cooperative  studies  or  regulations  had  been  applied,  not- 
withstanding the  fact  that  the  mode  of  life  and  distribution  of 
population  and  industries  are  more  favorable  than  in  American 
cities.     The  average  weight   of  cars   in  foreign  cities  is  essen- 


80 


EUROPEAN   PRACTICE 


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EUROPEAN   PRACTICE  81 

tially  less  than  in  most  American  cities  of  the  same  popu- 
lation and  the  tramway  traffic  and  loads  per  capita  may  be 
one-fifth  or  even  less  in  Europe  than  in  America.  A  city  like 
Berlin  with  over  2,000,000  inhabitants  handles  all  its  trans- 
portation with  a  maximum  load  of  about  30,000  k.w.  (Chicago 
and  the  adjacent  territory  with  2,600,000  population  requires 
a  maximum  load  of  about  200,000  k.  w.)  Manchester  with 
a  population  of  1,250,000  and  Glasgow  with  1,000,000  have 
traction  loads  of  11,000  k.  w.  and  11,500  k.  w.  respectively. 
(Boston  and  the  surrounding  territory  served  by  the  same  trac- 
tion system  has  an  approximate  population  of  1,150,000  and 
requires  a  power  station  capacity  of  75,000  k.  w.)  Milan  with 
a  population  of  over  600,000  inhabitants  has  a  traction  load 
of  approximately  8,000  k.  w.  and  Niirnberg  with  350,000 
inhabitants  uses  only  1000  k.  w.  (The  city  of  Worcester, 
Mass,  with  a  population  of  approximately  160,000  requires 
power  station  capacity  of  7,500  k.  w.)  These  comparisons 
should  not  be  taken  as  a  definite  index  to  comparative  elec- 
trolysis conditions  since  many  other  factors  are  involved. 

Other  similar  statistics  for  smaller  places  are  given  in 
Figure  6,  and  they  should  be  taken  in  consideration  in  applying 
to  this  country  'the  results  of  this  investigation  of  foreign  prac- 
tice. Regardless  of  the  degree  of  improvement  -which  economical 
limitations  may  make  permissible  to  accomplish  in  local  situa- 
tions, the  fundamentals  for  the  solution  of  the  electrolysis 
problem  evolved  abroad  merit  the  most  careful  study  to 
ascertain  their  possible  application  to  American  conditions. 


G.  REGULATIONS  ADOPTED  AND  PROPOSED. 

78.  Germany — Earth  Current  Commission's  Recommenda- 
tions. Recommendations  of  the  German  Earth  Current  Com- 
mission as  adopted  by  the  Gas,  Water  and  Railway  Interests  of 
Germany. 

Regulations  for  the  protection  of  gas  and  water  mains 
from  the  electrolytic  action  of  currents  from  direct  current 
Electric  Railways  which  use  the  rails  as  a  return. 

Accepted  for  two  years  at  the  yearly  meeting  of  1910 
and  for  a  further  two  years  at  the  yearly  meeting  of  1912. 

Published  in  the  Electrotechnische  Zeitschrift  1910, 
page  491,  and  1911,  page  511. 


82  EUROPEAN   PRACTICE 

SECTION  1.     APPLICATION  OF  RULES. 

The  following  rules  govern  the  installation  of  direct  current 
railways  or  sections  of  direct  current  railways  which  use  the 
rails  for  carrying  the  return  current.  Unless  otherwise  men- 
tioned the  herein  given  admissible  potential  values  should  be 
adhered  to  when  laying  out  new  railways.  For  determining 
the  resistance  of  a  line,  the  rails  only  must  be  taken  into  ac- 
count as  current  carrying  mediums  and  the  assumed  resistance 
of  the  rails,  as  well  as  the  assumed  percentage  increase  of  re- 
sistance due  to  the  bonding,  must  be  stated. 

These  values  must  not  be  exceeded,  either  when  making  the 
necessary  calculations  or  by  the  plant  when  in  actual  normal 
operation. 

These  rules  do  not  apply  when  railways  are  laid  with 
special  track  or  when  the  rails  are  laid  on  wooden  sleepers, 
in  which  case  there  is  generally  an  air  clearance  between  the 
rails  and  the  stone  ballast.  But  the  rules  do  apply  if  this 
air  clearance  does  not  exist,  as  at  grade  crossings,  unless  an 
equivalent  insulation  is  provided  for  locally.  Further,  these 
rules  do  not  apply  to  railway  lines  which  do  not  approach 
closer  than  200  meters  to  an  underground  pipe  network. 

EXPLANATION.* 

The  regulations  apply  only  to  direct  current  railroads  or 
sections  of  such,  using  the  rails  as  conductors.  Railroads  not 
using  the  rails  as  conductors  are  eliminated  from  the  start, 
because  the  same  do  not  send  any  currents  into  the  earth  and 
therefore  cannot  have  any  damaging  influence  on  the  pipes. 
According  to  the  experience  reached  so  far,  alternating  current 
seems  to  have  very  little  effect,  so  that  any  extension  of  these 
rules  to  cover  also  alternating  current  railways  does  not  seem 
justified.  At  any  rate,  the  conditions  produced  by  alternating 
current  railways  are  not  yet  sufficiently  understood  to  allow  of 
establishing  any  restrictions  in  regard  to  their  equipment  and 
operation  for  the  protection  of  pipes. 

In  case  a  railroad  is  operated  partly  with  direct  current 
and  partly  with  alternating  current,  these  regulations  apply 
only  to  those  sections  the  rails  of  which  carry  direct  current. 
The  fixed  upper  limits  of  permissible  potentials  apply  to  the 
design  of  the  plant,  unless  otherwise  stated,  and  in  the 

*NOTE:  This  explanation  and  the  others  following  are  included  in  the 
German  Earth  Current  Committees  Recommendations. 


EUROPEAN   PRACTICE  83 

calculations  only  the  rails  and  the  bonds  are  to  be  considered 
as  far  as  the  conductivity  and  the  resistances  of  the  conductors 
are  concerned.  The  assumed  resistance  of  the  rails  and  the 
increase  of  same  by  the  resistance  of  the  bonds  is  to  be  stated, 
and  such  limiting  values  are  not  to  be  exceeded  either  by  cal- 
culations or  in  practice. 

The  earth  as  a  shunt  is  not  considered.  Through  contact 
of  the  rail  network  with  the  ground,  a  part  of  the  current  passes 
into  the  ground  and  the  potentials  of  the  rail  network  are 
thereby  lowered  as  compared  with  a  case  of  perfect  insulation 
from  the  ground,  the  effect  becoming  greater,  the  more  the 
current  passes  into  the  ground.  It  is,  therefore,  not  correct 
to  take  the  differences  of  potentials  as  found  immediately 
after  the  construction  of  a  rail  network  as  a  basis  for  estimating 
the  safety  against  damaging  influences,  but  it  is  necessary  to 
go  back  to  the  first  cause,  that  is  to  say,  the  differences  of 
potential  as  they  would  be  if  the  rails  were  completely  insulated. 

This  rule  allows  of  an  exact  calculation  of  the  conditions 
during  the  design  of  the  plant  without  any  uncertain  and 
varying  values  for  different  localities.  The  limit  values  are 
not  to  be  exceeded  either  during  the  calculations  or  at  the 
actual  practical  test.  The  method  of  the  practical  test  will 
be  discussed  in  Section  3.  The  projection  of  the  plant  is, 
therefore,  to  be  based  on  assumptions  as  correct  as  possible 
with  regard  to  the  resistance  of  the  rail,  the  cables,  and  the 
consumption  of  current,  and  it  is  advisable  to  consider  also  a 
later  increase  of  the  traffic. 

Railroads,  the  rails  of  which  are  insulated  on  special  road- 
beds, generally  have  such  a  great  resistance  against  the  earth 
that  passage  of  current  into  the  ground  to  be  considered  as 
dangerous  to  pipes  does  not  occur.  Higher  potentials,  there- 
fore, are  permissible  for  such  railroads,  assuming  that  a  suffi- 
cient insulation  is  provided  for  also  on  grade  crossings,  etc. 

As  a  means  to  this  end  are  to  be  considered: 

Insulating  strata  between  rails  and  ground,  for  instance, 
tar  paper,  which  must  extend  on  aU  sides  sufficiently  beyond 
the  place  in  question;  or  the  surrounding  of  the  pipes  with 
insulating  material.  Such  places  are  to  be  inspected  from  time 
to  time  to  ascertain  the  effect  of  such  insulation. 

For  the  exemption  from  these  regulations  the  laying  of  the 
rails  on  a  special  roadbed  is  required,  because  it  is  only  in  this 
way  that  a  permanent  insulation  can  be  reached  and  main- 


84  EUROPEAN   PRACTICE 

tained.  About  the  details  of  the  system  of  insulation  to  be 
used,  no  rules  were  issued.  A  lasting  insulation  is  to  be  guar- 
anteed by  the  way  in  which  the  rails  are  laid.  The  laying 
of  rails  on  wooden  ties  as  mentioned  above  is  intended  as  an 
example  only.  At  any  rate  to  secure  satisfactory  insulation 
it  is  imperative  that  the  rails  be  nowhere  in  contact  with  the 
moisture  of  the  ground,  as  this  greatly  favors  the  passage  of 
the  current  into  the  ground. 

Tracks  which  are  at  all  points  at  least  200  m.  distant  from 
any  pipes  are  exempt,  because  any  current  coming  over  such 
an  extended  area  spreads  to  such  a  degree  that  its  density 
cannot  possibly  be  harmful.  In  this  respect  concession  has 
been  made  to  long  outlying  railway  lines  because  the  subjection 
of  such  to  these  regulations  would  entail  great  economic  disad- 
vantages in  certain  cases.  The  maintenance  of  good  con- 
ductivity on  such  outlying  sections  is  to  be  strongly  recom- 
mended so  as  to  prevent  the  return  currents  from  reaching  a 
dangerous  density  where  such  sections  join  the  rails  of  an 
inner  rail  network,  i.e.,  a  density  exceeding  the  limit-  given 
in  Section  5. 

SECTION  2.     RAIL  CONDUCTORS. 

All  rails  serving  as  return  conductors  should  be  built  with 
regard  to  this  requirement,  should  be  made  as  good  conductors 
as  possible  and  should  always  be  kept  in  good  order. 

The  percentage  of  increase  of  the  resistance  of  a  given  length 
of  track  due  to  the  bonding  should  not  exceed  the  value  as- 
sumed when  laying  out  the  railway,  and  must  not  be  more  than 
20%  more  than  the  resistance  of  the  same  length  of  track  if  the 
rails  were  without  joints  and  of  the  same  cross  section  and  the 
same  specific  conductivity.  On  laying  out  a  railway  line  con- 
sisting of  main  and  auxiliary  rails,  the  combined  cross  section 
of  both  rails  can  only  be  taken  into  account  when  determining 
the  resistance  of  the  track,  provided  the  auxiliary  as  well  as  the 
main  rails  are  properly  bonded  and  cross  bonded. 

At  rail  crossings  and  at  switches,  the  rails  must  be  well 
bonded  by  special  bridge  bonds. 

On  single  tracks  as  well  as  on  lines  where  several  tracks  are 
lying  side  by  side  the  rails  must  be  efficiently  cross  bonded 
and  these  cross  and  bridge  bonds  must  have  a  conductivity 
at  least  equal  to  a  copper  conductor  of  80  square  millimeters. 

At   all  movable   bridges   or  similar  structures   which  neces- 


EUROPEAN   PRACTICE  85 

sitate  an  interruption  of  the  rails,  special  insulated  conductors 
have  to  be  provided  which  secure  a  continuous  connection 
between  the  two  rail  ends.  In  such  cases,  the  voltage  drop 
at  average  load  must  not  exceed  5  millivolts  for  each  meter 
distance  between  the  interrupted  rails. 

All  current  carrying  conductors  which  are  connected  to  the 
rails,  must  be  insulated  from  earth,  excepting  short  connec- 
tions such  as  bonds,  cross-bonds  and  bridge-bonds  at  switches 
and  turntables.  If  such  bonds  are  laid  not  deeper  than  25 
centimeters  into  the  earth,  they  may  be  bare  conductors. 

EXPLANATION. 

The  first  condition  for  the  reduction  of  stray  currents  and 
for  the  effectiveness  of  all  the  proposed  precautionary  meas- 
ures, is  the  good  conductivity  of  the  tracks  and  the  maintenance 
of  this  conductivity.  High  resistances  of  the  single  sections 
cause  an  increase  of  the  current  passing  into  the  ground.  The 
maintenance  of  the  good  conductivity  of  the  rails  also  is  to  the 
economic  interest  of  the  railroad,  because  a  bad  conductivity 
will,  under  certain  circumstances,  cause  loss  of  energy. 

It  is  not  desirable  to  issue  rules  concerning  the  cross-sections 
of  rails  or  for  the  conductivity  of  the  steel  because  the  cross- 
section  and  the  chemical  composition  of  the  steel  are  both 
determined  by  mechanical  considerations;  the  conductivity  is 
dependent  on  the  composition  of  the  steel,  while  the  conductance 
of  the  rail  depends  on  both  the  conductivity  and  the  profile. 

The  resistance  of  a  rail  network  is  widely  influenced  by  the 
quality  of  the  electrical  connections  of  the  rails  at  their  joints. 

The  rules  do  not  recommend  one  or  another  system  of  con- 
nections at  the  joints,  but  give  data  covering  the  permissible 
increase  of  the  resistance  by  such  connections. 

In  consideration  of  the  varying  resistance  of  rails  of  dif- 
ferent profile,  it  is  not  possible  to  establish  a  uniform  per- 
missible resistance  for  a  bond,  but  the  permissible  increase  of 
the  total  resistance  of  a  section  by  all  the  bonds  is  given. 
This  increase  must  not  be  over  20%.  Inside  of  these  limits 
the  designing  engineer  may  assume  any  increase  of  the  re- 
sistance by  the  bond,  but  it  must  be  considered  that  the  increase 
assumed  must  be  permanently  maintained  later  on  (Compare 
Sections  6  and  3). 

It  will  be  well  to  assume  during  the  design  of  the  plant, 
the  increase  of  resistance  of  the  bonds  as  very  near  the  per- 


86  EUROPEAN   PRACTICE 

missible  limit.  This  is  very  important  when  shorter  rails  are 
to  be  used,  with  the  consequent  greater  number  of  joints,  the 
maintenance  of  which  is  correspondingly  more  difficult  and, 
therefore,  an  increase  of  resistance  through  deficient  bonds  to 
be  expected.  The  conductivity  of  rails  is  to  be  ascertained 
on  a  number  of  samples  before  the  rails  are  laid,  so  as  to  have 
a  guarantee  that  the  calculated  resistance  will  correspond  to 
the  resistance  of  the  finished  network. 

The  measurement  of  the  resistance  is  made  by  measuring 
the  current  and  the  potential  on  a  rail  as  long  as  possible  and 
insulated  from  its  supports;  the  potential  terminals  should 
include  a  part  of  the  circuit  between  the  current  contacts  and 
they  should  be  at  least  of  0.5  meter  distant  from  these  current 
contacts.  A  simple  calculation  gives  the  conductivity  of  the 
rail  by  using  the  value  shown  by  ammeter  and  voltmeter. 
The  conductivity  of  the  rails  now  in  use  is  generally  found  to 
be  between  4  and  5.5  Siemens. 

In  cases  where  main  and  auxiliary  rails  are  to  be  used  and 
where  the  combined  cross- section  of  both  is  taken  into  cal- 
culation, *  the  conductivity  of  the  auxiliary  rail  also  is  to  be 
measured  as  the  same  may  differ  considerably  from  the  con- 
ductivity of  the  main  rail. 

At  crossings  and  switches  a  loosening  of  the  rail  connections 
will  take  place  caused  by  the  vibrations  brought  about  by  the 
passage  of  the  rolling  stock,  for  which  reason  such  places  are 
to  be  bridged  specially  by  electrical  conductors.  The  cross 
connections  serve  the  purpose  of  eliminating  differences  of 
potentials  between  tracks  running  side  by  side  and  also  to 
insure  a  good  metallic  connection  between  the  rails  on  one  side 
of  a  track  in  the  case  of  a  temporary  low  conductivity  of  single 
joints  or  interruptions. 

It  seems  advisable  in  consideration  of  the  different  length  of 
rails,  not  to  give  an  absolute  distance  between  the  cross-con- 
nections, but  to  establish  their  number  by  the  number  of  joints. 
The  bonds  and  cross-connections  may  be  of  any  material  as 
long  as  their  conductivity  reaches  at  least  that  of  a  copper 
connector  of  80  square  mm.  For  the  connection  of  interrupted 
tracks,  as  for  instance  at  movable  bridges,  insulated  cables  are 
required  because  of  the  presence  of  water  or  other  substances 
in  the  soil,  which  highly  favor  the  passage  of  currents  into 
the  ground.  The  highest  permissible  drop  in  potential  at 
average  load  has  been  fixed  at  5  millivolts  per  meter  distance 


EUROPEAN   PRACTICE  87 

between  the  places  of  interruption,  to  insure  a  small  difference 
of  potential  between  these  points. 

Furthermore  care  is  to  be  taken  that  the  tracks  in  a  movable 
bridge  are  in  good  contact  with  the  tracks  on  both  sides  of  it. 
The  following  is  an  example  of  the  calculation  of  a  cable  bridg- 
ing across  the  gap. 

When  the  distance  between  the  tracks  at  the  point  of  inter- 
ruption equals  30  meters,  the  permissible  difference  of  potential 
therefore  is  5  X  30  which  equals  150  millivolts.  The  current 
to  be  carried  across  is  assumed  to  be  120  amperes  and  the 
length  of  cable  30  meters.  Assuming  a  specific  resistance  of 
17.5  milliohms  per  meter  and  square  millimeter,  the  resulting 
cross-section  is : 

17.5  XL/  17.5  X  30  X  120 

q-  —  -115-  :420sq.mm. 

Inasmuch  as  the  increase  of  the  surface  contact  between 
the  conductors  and  ground  results  in  an  increase  of  the  cur- 
rent passing  from  the  conductors  into  the  ground,  the  con- 
ductors connected  to  the  rails,  especially  those  lying  deep 
enough  to  come  into  contact  with  the  moisture  of  the  ground, 
are  to  be  insulated  conductors.  Only  short  connections  such 
as  jumpers  on  crossings  and  switches,  are  exempt  from  this 
rule  on  account  of  the  same  not  lying  deeper  than  25  cm. 
under  the  surface,  which  means  that  they  hardly  come  into 
contact  with  the  moisture  of  the  ground.  The  increase  of 
surface  of  the  contacts  with  the  ground  by  these  conductors, 
is  too  small  in  proportion  to  the  total  surface  of  the  rail  net- 
work to  cause  any  apprehension  regarding  the  currents  passing 
into  the  ground. 

SECTION  3.     RAIL  POTENTIAL. 

A  railway  network  is  divided  into  two  sections,  first,  the 
open  road  connecting  the  various  townships,  and  second,  the 
urban  network. 

In  the  urban  network  and  for  a  distance  of  2  km.  beyond, 
the  voltage  drop  between  any  two  rail  points  should  never 
exceed  2.5  volts  when  the  line  is  working  under  normal  con- 
ditions, and  the  drop  in  the  rails  for  each  kilometer  of  open  road 
should  not  exceed  1  volt.  Occasional  night  cars  are  not  to  be 
considered  in  determining  the  average  load. 

In  townships  through  which  only  a  single  line  is  run,  without 


88  EUROPEAN   PRACTICE 

local  rail  network,  the  total  voltage  drop  in  the  rails  must  not 
exceed  2.5  volts  from  end  to  end  of  the  township's  pipe  network. 

Any  apparatus  which  is  supplied  with  current  and  which  is 
connected  to  the  railway  network  must  not  increase  the  volt- 
age drop  above  the  stated  limits. 

If  various  railway  systems  are  connected  together  either 
through  the  medium  of  the  rails  or  through  the  power  station, 
each  system  must  fulfill  the  above  conditions.  A  rail  system 
in  a  township  with  an  independent  pipe  network  has  to  comply 
with  the  above  regulations  also. 

Exceptions  from  these  rules  in  regaid  to  the  voltage  drop  in 
a  railway  network  are  admissible  if  local  conditions  and  service 
necessitate  and  justify  such  exceptions.  If,  for  instance,  the 
service — as  is  the  case  in  freight  yards — covers  only  a  small 
portion  of  the  day,  the  above  limits  of  rail  drops  may  be  ex- 
ceeded. In  yards  with  a  service  up  to  3  hours  daily,  double 
the  above  values  are  permitted,  and  with  a  service  up  to  one 
hour,  four  times  the  above  values  are  allowed. 

EXPLANATION. 

As  mentioned  in  Section  1,  the  rail  network  is  to  be  con- 
sidered as  insulated  from  the  ground,  so  that  the  earth  as  a 
shunt  is  not  considered. 

The  resistances  of  the  single  sections  are  to  be  calculated 
from  the  resistance  of  the  rails  under  observance  of  the  rules 
in  Sections  1  and  2. 

For  the  calculation  of  the  potentials  the  value  of  the  average 
current  is  to  be  used,  as  the  magnitude  of  electrolytic  decom- 
position of  the  pipe  metal  depends  on  the  quantity  of  current, 
that  is  to  say,  the  product  of  current  and  time.  The  highest 
values  have  not  to  be  considered  for  the  calculations.  To  find 
the  consumption  of  current  the  average  service  as  per  schedule 
has  to  serve  as  the  base. 

The  average  current  consumed  on  single  sections  can  be 
calculated  from  the  number  of  car  km.  or  ton  km.  to  be  covered, 
by  using  the  value  for  the  consumption  of  current  which,  ac- 
cording to  experience,  and  in  consideration  of  the  local  con- 
ditions, is  used  for  one  car  km.,  or  ton  km. 

But  it  is  also  permissible  to  distribute  the  consumption  of 
current  over  the  whole  net  in  a  way  corresponding  to  the  loca- 
tions of  the  single  trains  at  the  time  of  the  average  load  and  to 
calculate  for  each  train  the  consumption  of  current  taking  into 


EUROPEAN   PRACTICE  89 

consideration  the  weight  of  the  cars,  the  speed  and  operating 
conditions  (grades,  stops). 

In  regard  to  the  schedule,  the  difference  between  summer 
and  winter  service  is  to  be  considered.  The  increase  at  regular 
intervals,  as  for  instance  on  Sundays,  is  to  be  taken  into  ac- 
count. Small  deviations  from  the  schedule,  as  for  instance, 
single  night  cars,  or  auxiliary  cars,  shall  not  be  considered, 
because  the  first  would  reduce  the  average  value  out  of  pro- 
portion, and  the  frequency  of  the  second  cannot  be  estimated 
at  the  time  of  the  calculations  and  otherwise  are  not  of  any 
appreciable  influence  on  the  final  results. 

It  is  impossible  to  get  regulations  embracing  all  conditions 
and  possibilities  and  it  is  therefore  necessary  to  consider  all 
peculiarities  of  a  plant  during  its  projection.  If  there  are  any 
additional  places  connected  to  the  rails,  where  current  is  used 
for  stationary  motors,  station  lighting,  etc.,  these  are  to  be  con- 
sidered. 

After  the  drops  in  potential  on  the  central  sections  have 
been  tabulated,  based  on  the  above  calculations,  the  distribu- 
tion of  the  potential  in  the  rail  network  can  be  found.  In 
addition  to  the  foregoing  data  for  the  calculation  of  the  drop 
in  potential  on  the  single  sections,  consideration  is  to  be  given 
to  the  proposed  return  cables  and,  in  case  of  a  three  wire  system, 
to  the  direction  of  the  current  in  the  districts  of  different  polarity. 

Difference  in  potential  between  any  two  points  of  the  rail 
network  must  answer  the  following  conditions: 

Around  every  individual  pipe  network  (meaning  a  network 
not  in  metallic  contact  with  any  other  network)  and  also 
around  single  pipes,  a  zone  of  two  hundred  m.  is  to  be  circum- 
scribed and  all  tracks  lying  outside  of  this  zone  are  not  to  be 
considered  in  connection  with  these  regulations,  as  per  last  part 
of  Section  1. 

For  each  *of  the  rail  branches  lying  inside  of  these  individual 
pipe  networks,  the  following  rules  apply: 

If  there  are  any  branches  of  the  railroad  inside  of  a  pipe  net- 
work, including  the  200  m. -zones,  a  belt  2  km.  wide  is  to  be 
laid  around  the  inner  rail  network.  Inside  this  belt  the  po- 
tential of  the  rails  between  any  different  points  must  nowhere 
exceed  2.5  v.,  as  long  as  no  portion  of  the  rails  is  more  than 
200  m.  distant  from  the  nearest  pipe  along  its  total  length 
(Compare  Fig.  7.). 

On  the  sections  outside  the  2.5  v.  districts,    the    drop    in 


90  EUROPEAN   PRACTICE 

potential  must  not  exceed  1  v.  per  km.  This  applies  to  out- 
lying sections  which  are  shown  in  Fig.  7  by  heavy  dotted 
lines. 

In  the  case  of  a  railroad  with  no  branches  (country  roads) 
and  a  pipe  network,  the  drop  in  potential  inside  the  pipe  net- 
work must  not  exceed  2.5  v.  (Compare  Fig.  8).  The  rule 
establishing  a  drop  of  1  v.  per  km.  states  that  the  current  in 

the  track  must  not  exceed  •==-„  if    W   is    the    resistance    of    the 

W 

track  in  ohms  per  km.  For  a  uniform  load  of  a  section  of  L 
km.  length  and  a  uniform  resistance,  the  permissible  drop  in 

potential  =  ~~  v-  i-e-  9"   drop  in  one  rail.     The  calculation  of 

this  drop  also  is  based  on  the  average  load,  according  to  the 
schedule. 

Strict  rules  have  been  issued  for  the  interior  rail  network 
with  its  many  branches,  as  it  mostly  covers  the  same  area  as 
the  pipe  network.  This  has  been  done  in  consideration  of 
the  greater  surface  of  contact  between  ground  and  rails  and 
pipes  respectively  which  increases  the  probability  of  a  passage 
of  current  through  the  ground.  The  potential  of  2.5  volts 
for  this  district  has  been  judged  permissible  because,  according 
to  the  results  of  previous  investigations,  it  is  to  be  assumed 
that  this  potential  will  not  under  ordinary  conditions  cause 
any  danger  to  pipe  lines  beyond  the  practical  limits.  To  avoid 
as  much  as  possible  any  greater  concentrations  of  ground  and 
pipe  currents  at  the  outlying  sections  which  immediately  join 
the  inner  rail  network,  and  where  important  parts  of  the  pipe 
network  often  extend,  strict  rules  have  been  issued  covering 
the  district  inside  the  2  km.  belt  around  the  inner  rail  network. 

For  the  outlying  section  an  economical  advantage  has  been 
contemplated  by  limiting  the  drop  in  potential  to  1  v.  per  km. 
Railroads  interconnected  by  their  rail  networks  or  by  a  common 
power  plant  are  to  be  considered  as  one  system  because  such 
railroads  influence  each  other,  inasmuch  as  equalizing  currents 
will  flow  between  their  rail  networks. 

Deviations  in  both  directions  from  these  potentials  can  be 
justified  by  certain  circumstances — in  case  of  especially  good 
conditions  of  the  ground,  that  is  to  say,  in  very  dry  dirt  an 
increase  of  the  potentials  may  be  permissible.  But  even  in 
such  cases  it  is  advisable  to  be  cautious  in  allowing  such  an 


EUROPEAN   PRACTICE 


District  of  interior  pipe  -  network. 

District  of  200  rn.  around  pipes  with  no  branches. 

Railroads  in  the  2.5  V.  District. 

Railroads  in  the  IV-Km  District. 

Railroads  with  no  Restrictions. 

Figure   7 


District  of  the  pipe -network  with  the  200m.  belt 

surrounding  it  and  the  pipes  with  no  branches. 

District  of  the  interior  Rail-network  with  the  2  Km. 

belt  surrounding  it. 

Railroads  in  the  2,5  V.  District  (shaded  by  both 

horizontal  and  vertical  lines). 

Railroads  in  the  IY-Km.  District  (shaded  by 

horizontal  lines). 

Railroads  with  no  restrictions  (not  shaded,  or  by 

vertical  lines  only). 

Figure  8 


92  EUROPEAN   PRACTICE 

increase,  so  as  not  to  violate  the  rules  as  given  in  paragraph  5. 
Where  the  conditions  are  unfavorable,  for  instance,  where 
moist  ground  of  especially  high  conductivity  prevails,  it  is 
advisable  to  remain  below  the  limits.  For  railroads  with  brief 
daily  operation  concessions  have  been  made  because  damage 
to  the  pipes  depends  upon  the  duration  of  the  influence  of  the 
current  so  that,  considering  the  short  time  of  operation,  even 
greater  currents  cannot  cause  any  appreciable  damage  to  the 
pipes. 

For  railroads  of  three  hours  daily  operation  double  drop  in 
potential  is  allowed,  while  for  railroads  of  one  hour  operation,  four 
times  the  drop  is  permissible.  Wherever  the  rail  network  is  not 
sufficient  to  carry  the  current  without  exceeding  the  per- 
missible potential  in  the  network,  the  whole  plan  for  the  return 
of  the  current  must  be  altered,  and  improvement  will  be  reached 
by  providing  return  cables  in  which,  if  necessary,  resistances 
or  boosters  may  be  inserted.  The  resistances  should  be 
variable  so  as  to  correspond  with  the  variable  conditions  of 
service  and  operation.  In  cases  where  the  railroad  "system 
is  fed  from  several  power  plants  a  reduction  of  the  drop  in 
potential  in  the  rails  may  be  brought  about  by  shifting  the 
loads  of  the  several  power  plants. 

The  arrangement  of  the  cables  and  resistances  can  be  made 
in  so  many  different  ways  as  to  make  a  general  rule  for  all 
cases  impossible.  It  is  recommended  to  investigate  thoroughly 
the  cases  under  observation,  because  considerable  saving  in  the 
construction  and  operation  of  the  plant  may  be  achieved  by  a 
careful  layout. 

The  keeping  of  the  return  points  at  the  same  potential  is 
recommended  as  a  precautionary  measure  but  not  required. 
The  same  offers  a  certain  guarantee  of  the  possibility  to  keep 
the  difference  of  potential  within  the  2.5  V.  limits. 

Furthermore,  the  use  of  the  3  wire-system  with  the  rails  as 
a  neutral  conductor  is  worthy  of  consideration.  In  this  sys- 
tem the  difference  of  potential  in  the  rails  depends  on  the  dis- 
tribution of  the  positive  and  negative  feeder  districts.  This 
distribution  again  depends  on  the  local  conditions  of  the  plant, 
so  that  no  general  rules  can  be  given  in  regard  to  it. 

Alterations  of  the  conditions  of  operation  can  be  counter- 
acted by  switching  the  load  to  the  positive  or  negative  side 
of  the  system.  The  rules  do  not  recommend  any  certain  sys- 
tem, but  leave  it  entirely  to  the  projecting  engineer  to  select 


EUROPEAN   PRACTICE  93 

the  one  best  adapted  to  existing  conditions.  The  damage  to 
pipes  takes  place  mostly  at  points  of  low  potential  on  two- 
wire  railroads,  in  the  neighborhood  of  the  return  points;  and 
on  three- wire  railroads,  in  the  districts  of  negative  feeders,  be- 
cause it  is  mainly  here  that  the  current  leaves  the  pipes. 
It  is  advisable  to  place  the  return  points  of  the  negative  feeder 
districts  whenever  possible  in  locations  with  dry  ground  of 
low  conductivity  and  as  far  as  possible  from  such  pipe  lines  as 
are  of  importance  for  the  water  and  gas  supply. 

The  permissible  limits  of  differences  in  potential  in  rails 
must  not  exceed,  either  according  to  calculations,  or  at  the 
practical  trial,  the  limits  given  in  Section  1  of  these  rules. 
The  measurement  of  the  difference  in  potential  is  made  by  means 
of  test  wires  as  called  for  in  Section  6.  The  measurements 
of  differences  in  potential  are  limited  to  those  points  which , 
according  to  the  calculations,  come  nearest  to  the  established 
limits.  Wherever  long  lines,  as,  for  instance,  telephone  wires, 
are  available,  it  is  advisable  to  use  them  for  these  measure- 
ments, otherwise  several  test  wires  may  be  connected  in  series 
or  temporary  test  lines  may  be  installed:  finally,  the  results 
of  single  measurements  may  be  computed  to  reach  the  same 
final  results.  Only  high  resistance  voltmeters  should  be  used 
for  these  measurements  so  as  to  make  the  resistances  of  the 
test  wire  and  contacts  negligible.  The  pointers  of  these  in- 
struments should  have  the  slowest  movements  and  a  good 
damper  arrangement,  so  as  to  give  good  readings  even  under 
strong  fluctuations.  For  all  measurements  only  average  values 
are  considered.  All  measurements  are  to  be  extended  over  a 
full  period  of  operation  which  results  from  the  average  frequency 
of  trains. 

SECTION  4.     RESISTANCE  BETWEEN  RAIL  AND  EARTH. 

The  resistance  between  ground  and  the  rail  which  is  used 
for  carrying  the  return  current  should  be  kept  as  high  as  pos- 
sible. When  the  conditions  of  the  ground  or  the  situation  of 
the  track  are  not  favorable  for  this  purpose,  the  resistance 
should  be  increased  by  a  special  effective  insulation. 

The  rails  or  any  conductor  connected  to  the  rails  must  not 
be  in  contact  with  the  pipes  or  any  kind  of  metal  buried  in 
the  ground.  Furthermore,  care  must  be  taken  that  the  dis- 
tance between  the  nearest  rail  and  any  metallic  part  of  the 
pipe  lines  or  connections  to  them  which  project  above  the  ground 


94  EUROPEAN   PRACTICE 

or  lie  near  the  surface,  be  kept  as  great  as  possible,  and  should 
never  be  less  than  one  meter. 

Stationary  motors,  lighting  installations  or  any  other  plant 
which  receives  current  from  a  railway  system  which  uses  the 
rails  for  carrying  the  return  current,  must  be  connected  to  the 
rail  network  by  means  of  insulated  conductors.  Except ed  are 
short  connections  of  not  more  than  16  square  millimeters  which 
are  not  deeper  than  25  centimeters  in  the  ground  arid  which 
are  at  a  distance  of  at  least  1  meter  from  any  part  of  a  pipe 
network.  These  connections  may  be  of  bare  metal.  In  order 
to  increase  the  resistance  between  rail  and  ground  it  is  recom- 
mended to  use  a  bedding  of  high  resistance  and  to  provide 
good  drainage,  also  to  render  the  bedding  water-tight  to  the 
roadbed  for  a  sufficient  width  on  both  sides  of  the  rail. 

The  use  of  salt  for  the  melting  of  snow  and  ice,  should  be 
limited  to  cases  of  absolute  necessity. 

Wherever  sufficient  distance  between  the  rail  and  such  parts 
of  the  pipe  line  as  project  above  the  surface  is  not  obtainable, 
it  is  advisable  to  change  the  pipe  run,  or  where  this  is  not  pos- 
sible, to  use  insulating  strata  (such  as  vitrified  clay,  masonry 
or  wooden  conduits,  etc.). 

EXPLANATION. 

The  magnitude  of  currents  passing  into  the  ground  depends 
not  only  on  the  potentials  in  the  rail  network,  but  also  on  the 
resistances  between  the  rails  and  the  pipes  and  on  the  resist- 
ances of  the  pipe  lines  themselves.  It  will  always  be  of  advan- 
tage to  increase  the  resistance  of  the  ground  between  the  rails 
and  the  pipes.  An  artificial  increase  of  the  resistances  of  the 
pipe  line  can  be  achieved  for  instance,  by  the  use  of  insulating 
flanges,  couplings,  etc.  Aside  from  the  technical  difficulties  of 
installing  such  insulating  parts  into  gas  pipes,  and  especially 
water  pipes  with  a  high  pressure,  and  of  insuring  their  lasting 
tightness,  it  would  be  difficult  to  provide  these  insulating 
pieces  in  the  necessary  numbers  and  to  take  care  of  their  correct 
distribution.  A  wrong  arrangement  of  the  same  will  lead  to  an 
extraordinary  concentration  of  currents  at  these  insulations 
with  consequent  corrosion  in  these  places.  A  greater  part  of 
the  drop  in  potential  between  pipe  and  rail  originally  takes 
place  in  the  roadbed  as  can  be  easily  understood  and  itistheie- 
fore  required  to  render  this  resistance  as  high  as  possible  by 


EUROPEAN   PRACTICE  95 

the  good  insulation  of  the  roadbed,  good  drainage,  etc.,  and  to 
maintain  it  thus. 

In  the  same  measure  that  the  increase  of  the  resistances 
between  rail  and  pipe  is  recommended,  the  use  of  any  means 
to  reduce  these  resistances,  is  to  be  warned  against.  Such 
means  to  be  considered  are  ground  plates,  connections  of  metals 
in  the  ground,  and  especially  metallic  connections  between  the 
.rails  and  the  pipes.  The  last  will  reduce  the  density  of  the 
current  at  the  point  of  connection  to  the  pipe,  but  they  cause 
an  increase  of  the  pipe  current  and  of  the  ground  currents  in 
general  which  may  cause  damage  in  other  places,  as,  for  in- 
stance, at  interruptions  in  the  pipe  line  or  at  crossings  with 
other  lines.  Any  local  measure  taken  must  be  considered  with 
regard  to  its  effect  on  the  pipes  in  other  localities. 

Metallic  connections  between  different  pipe  networks  also 
are  to  be  judged  from  this  viewpoint.  Immediate  contact  of 
any  parts  of  the  pipe  lines  with  the  rails,  or  too  close  an  ap- 
proach, has  the  same  effect  as  direct  metallic  connections  and 
is,  therefore,  to  be  avoided.  (By  a  re-location  of  rails  or  pipes 
or  installation  of  insulating  strata). 

Especially  in  cases  of  stationary  motors  or  lighting  plants 
connected  to  the  railroad  system,  there  exists  on  the  premises 
danger  of  an  accidental  or  deliberate  connection  or  contact 
with  the  pipe  lines.  It  is,  therefore,  necessary  to  have  strict 
rules  regarding  the  return  cables  from  such  plants. 

SECTION  5.     CURRENT  DENSITY. 

The  above  rules  are  intended  to  prevent  the  destruction  of 
the  pipes  by  electrolysis.  The  rate  of  destruction  is  in  direct 
proportion  to  the  amount  of  current  leaving  the  pipe. 

Any  pipe  line  where  the  current  leaving  the  pipe  exceeds  an 
average  density  of  0.75  milliampere  per  square  decimeter  and 
where  this  current  is  due  to  a  railway,  may  be  considered  en- 
dangered 'by  this  railway,  and  further  preventive  measures 
must  be  taken. 

For  railways  with  freight  service  when  the  service  is  of  com- 
paratively snort  duration,  exceptions  as  already  mentioned  are 
permissible. 

In  cases  where  the  current  leaving  or  passing  into  the  pipes 
changes  its  direction,  the  current  passing  into  the  pipe  must 
be  taken  as  nil  when  determining  the  average  density,  until 
further  experience  has  been  gained  in  this  matter. 


96  EUROPEAN   PRACTICE 

EXPLANATION. 

Inasmuch  as  a  total  elimination  of  all  damages  to  pipes  would 
be  in  most  cases  possible  only  at  a  disproportionately  high 
cost,  which  would  far  exceed  the  cost  of  any  possible  damage  to 
the  pipes,  it  is  necessary  to  allow  a  certain  limited  damage, 
that  is  to  say,  a  damage  which  is  of  little  practical  importance 
and  which  does  not  noticeably  shorten  the  life  of  the  pipes. 
These  rules  have  therefore  been  compiled  on  the  basis  of  the 
average  conditions,  that  is  to  say,  such  as  are  mostly  met  with, 
and  it  is  to  be  expected  according  to  previous  experience  that 
the  damage  done  to  pipe  lines  by  the  stray  currents  from  elec- 
trical railways,  generally  will  remain  limited  to  the  practical 
allowable  limit  wherever  these  rules  are  observed.  Under 
exceptionally  bad  conditions,  that  is  to  say,  under  conditions 
which  very  much  favor  the  origin  of  stray  currents,  greater 
corrosion  of  pipes  in  certain  places  can  hardly  be  avoided, 
even  if  the  limits  of  the  drop  in  the  potential  in  the  rails,  as 
laid  down  in  Section  3,  are  not  exceeded.  It  is,  therefore, 
advisable  to  establish  some  measure  for  the  elimination  of 
immediate  danger  to  the  pipes. 

For  the  judgment  of  the  damage  attributed  to  a  railroad 
system  the  density  of  the  current  leaving  the  pipes  and  return- 
ing to  the  railroad  system  is  indicative. 

The  density  of  the  current  at  the  pipe  can  be  measured  only 
after  the  completion  of  the  plant.  These  measurements  must 
be  made  during  the  time  of  operation,  as  per  schedule,  and  as 
described  in  Section  3.  The  average  density  is  important 
and  is  obtained  from  the  computation  of  the  results  of  several 
measurements,  each  of  which  follows  a  whole  period  of  service. 

Measurements  of  current  density  can  be  made,  for  instance, 
by  means  of  a  milliammeter  and  non-polarizable  frame  as  de- 
signed by  Prof.  Haber.  This  frame  contains  two  copper  plates 
which  are  insulated  from  each  other  and  which  foi  the  pre- 
vention of  polarization  are  covered  with  a  paste  of  copper 
sulphate  and  20%  sulphuric  acid,  over  which  a  parchment,  soaked 
with  sodium  sulphate  is  laid.  The  frame  is  filled  with  dirt 
except  between  the  plates,  and  placed  alongside  the  pipe  at 
right  angles  to  the  assumed  direction  of  the  current  and  then 
covered  with  dirt.  A  very  sensitive  ammeter  connected  to 
the  copper  plates  will  indicate  the  current  passing  through 
the  frame  and  the  density  of  this  current  can  readily  be  cal- 
culated by  taking  into  account  the  surface  of  the  copper  plates 


EUROPEAN   PRACTICE  97 

inside  the  frame.  Inasmuch  as  here  also  only  average  readings 
are  to  be  considered,  it  is  advisable  to  use  an  instrument  with 
very  slow  period. 

According  to  investigations  made  so  far,  absolute  danger  to 
the  pipes  results  whenever  the  density  of  the  currents  leaving 
the  pipes  reaches  the  average  value  of  0.75  milliampere  per 
square  dcm.  For  railroads  with  small  periods  of  operation 
an  excess  up  to  double  and  quadruple,  respectively,  the  above 
value  is  permissible  according  to  the  rules  laid  down  in  Sec- 
tion 3. 

Wherever  the  direction  of  the  current  changes,  the  currents 
entering  the  pipes  are  not  to  be  considered  in  the  calculations 
of  the  average  density,  inasmuch  as  it  is  not  as  yet  established 
that  such  currents  will  add  to  the  metal  of  the  pipes.  Wherever 
the  average  values  are  exceeded,  especial  precautionary  meas- 
ures are  to  be  taken,  the  nature  of  which  can  be  determined 
only  by  the  local  conditions.  In  many  cases  it  is  sufficient  to 
protect  a  very  limited  section  of  the  rail  network,  to  which 
end  the  further  reduction  of  the  drop  in  the  rails  may  not  be 
necessary,  but  which  may  be  attained  by  other  means  as,  for 
instance,  the  re-location  of  short  sections  of  tracks  or  pipes, 
or  the  artificial  increase  of  the  resistances  between  rails  and 
pipes  at  such  points. 

In  all  cases  the  question  arises  whether  the  railroad  is  to  be  con- 
sidered as  the  only  cause  of  current  concentration,  as  other  causes 
may  be  found  to  be  responsible  for  a  part  of  the  current  on  the 
pipes;  for  instance,  bare  neutrals  or  poor  insulation  in  other 
electrical  systems,  the  natural  electrical  elements  resulting 
from  the  use  of  different  metals  in  the  pipe  lines,  or  from  dif- 
ferent chemicals  in  solution  in  the  ground.  That  part  of  the 
current  which  is  attributable  to  the  influence  of  the  railroad 
can  be  determined  by  comparison  with  the  measurements  of  the 
current  during  the  period  of  no  operation.  In  many  cases  the 
influence  of  the  railroad  can  be  judged  from  contemporaneous 
measurements  of  current  density  and  the  potential  between 
pipe  and  rail.  Under  certain  circumstances  it  is  possible  to 
find  the  degree  of  influence  of  the  railroad  and  of  other  electrical 
plants  operating  at  the  same  time,  by  establishing  the  course 
of  the  current  in  the  ground.  For  this  investigation  elec- 
trodes that  cannot  be  polarized  are  used  as  contacts  from  the 
test  line  to  the  ground.  The  measurements  should  preferably 
be  made  by  the  potentiometer  method  in  order  to  eliminate 


98  EUROPEAN   PRACTICE 

drop  at  the  electrodes  due  to  the  current  flow,  but  this  method 
is  difficult  in  practice  on  account  of  the  rapid  fluctuations  of 
the  voltage.  It  will  be  sufficient  in  most  cases  to  make  the 
measurements .  with  a  voltmeter  of  very  high  resistance  so  that 
the  current  passing  through  the  electrodes  will  be  very  small. 
It  should  be  emphasized  that  such  measurements  should  be  made 
by  experts  only,  as  deviations  from  the  right  method  which 
seem  of  no  importance  often  give  useless  results. 

SECTION  6.     CONTROL. 

In  order  to  be  able  to  test  the  potential  at  t'he  return  points 
of  the  rail  system  of  a  given  territory,  pilot  wires  are  to  be 
connected  to  these  points  and  carried  to  a  central  testing  place. 

Before  a  service  may  be  increased  the  potential  distribution 
in  the  rail  network  must  be  retested. 

The  rail  bonds  and  bridge  connections  are  to  be  retested 
once  yearly  by  means  of  a  suitable  rail  joint  tester  and  must  be 
arranged  so  that  they  fulfill  the  rules  of  Sections  1  and  2.  Con- 
nections the  resistance  of  which  has  been  found  greater  than 
that  of  an  uninterrupted  rail  of  10  meters  length  must  be  re- 
paired to  comply  with  these  rules. 

EXPLANATION. 

The  control  of  the  drop  in  potential  in  the  whole  network 
would  be  best  assured  by  the  installation  of  test  wires  from 
one  of  the  buses  to  all  points  of  probable  highest  and  lowest 
rail  potential,  which  arrangement  admits  of  immediate  measure- 
ment of  potential  between  these  points. 

In  certain  cases,  especially  in  existing  plants,  the  installation 
of  such  test  wires  would  involve  great  cost.  Such  test  wires 
from  all  of  the  important  rail  points  were  not  required;  but  it 
has  been  ruled  that  all  points  of  the  rail  network,  to  which 
cables  of  the  same  district  are  now  connected,  are  to  be  pro- 
vided with  tes't  wires  which  have  to  run  to  some  central  point 
where  readings  of  the  differences  of  potentials  between  the 
return  points  can  be  taken. 

Wherever  .the  expense  involved  permits,  it  is  recommended 
to  install  test  wires  not  only  to  the  return  points  but  also  to 
the  points  of  highest  rail  potentials. 

After  permanent  changes  in  the  operation,  the  distribution 
of  the  potential  in  the  rail  network  is  to  be  investigated  in  the 
same  way  as  after  the  inauguration  of  the  plant,  in  order 


EUROPEAN   PRACTICE  99 

to  ascertain  whether  the  new  conditions  still  correspond  to 
the  rules. 

In  case  of  temporary  changes  of  short  duration  in  the  whole 
network  or  parts  of  the  same  as,  for  instance,  occasionally 
some  festival,  change  or  repair  of  tracks,  fairs,  exhibits,  etc., 
no  special  measures  are  to  be  taken  because  the  short  duration 
of  the  influence  will  cause  no  noticeable  damage  even  when 
the  limits  of  these  rules  are  exceeded. 

The  yearly  investigation  of  the  rail  joints,  as  required  by  the 
rules,  is  also  to  be  recommended  with  regard  to  the  reduction 
of  losses  of  energy.  For  these  measurements  an  apparatus 
may  be  used  which  allows  of  the  comparison  of  the  drop  in 
potentials  across  the  joint  with  one  of  the  adjoining  uninter- 
rupted rails  so  that  the  measurement  may  be  taken  during  the 
operation.  Joints  of  a  resistance  higher  than  that  of  an  un- 
interrupted rail  of  10  m.  length  are  immediately  to  be  repaired. 
The  total  resistance,  as  found  by  the  measurement  of  the 
single  joints,  must  not  exceed  the  value  which  has  been  as- 
sumed during  the  projection  of  the  plant  (compare  Section  2, 
paragraph  2) . 

Should  it  result  during  operation  that  rail  joints  are  of  a 
higher  resistance  than  that  assumed  in  the  designing  it  is 
permissible  to  abstain  from  a  re-construction  of  the  joints 
as  long  as  the  permissible  difference  of  potentials  in  the  rails 
is  not  exceeded,  even  with  these  higher  resistances.  The 
established  limits  of  20%  increase  of  the  resistance  of  the 
uninterrupted  rail  by  the  bonds  must  not  be  exceeded  in  any 
case. 

79.  France — Regulations    by    Minister    of    Public    Works 

Circular  and  order  of  the  Minister  of  Public  Works  (France) 
of  March  21,  1911,  establishing  the  technical  conditions  which 
electrical  distribution  systems  must  satisfy  in  order  to  conform 
to  the  law  of  June  15,  1906.  (Pages  25-27) 

SECTION  III.     REGULATIONS  RELATIVE  TO  THE  CONSTRUCTION 
OF  STRUCTURES  FOR  ELECTRIC  RAILWAYS  USING  DIRECT 

CURRENT.1 
DISTRIBUTION   POTENTIAL    FOR   RAILWAYS. 

ART.  27.  The  requirements  of  art.  3,  paragraph  4;  of  art.  5 
paragraph  26;  4  and  6  of  art.  25,  and  of  the  first  two  sections 


100  EUROPEAN   PRACTICE 

of  paragraph  3  of  art.  31  do  not  refer  to  trolley  wires,  nor  their 
supports,  nor  the  other  lines  placed  upon  these  supports,  nor 
those  not  upon  the  public  highway,  nor  those  inaccessible  to 
the  public,  if  the  potential  between  these  conductors  and  ground 
is  not  greater  than  1000  volts. 

1.  Electric  traction  projects  using  alternating  current  should  be  sub- 
mitted to  the  Minister  of  Public  Works  in  all  cases  where  discribution  is 
upon  the  public  highway. 

RIGHT  OF  WAY. 

ART.  28.  When  the  rails  are  used  as  conductors,  all  necessary 
measures  should  be  taken  to  guard  against  the  harmful  action 
of  stray  currents,  on  metallic  structures,  such  as  the  tracks 
of  railways,  the  water  and  gas  pipes,  the  telegraph  or  tele- 
phone lines  and  all  other  electric  conductors,  etc. 

To  this  end  the  following  regulations  shall  be  applied: 

1.  The  conductance  of  the  tracks  shall  be  known  to  be  in 
the  best  possible  condition,  especially  in  regard  to  the  joints, 
whose  resistance  should  not  exceed,  in  each  case,  that  of  10 
meters  of  the  normal  track. 

The  management  is  required  to  verify  periodically  this  con- 
ductance and  to  place  the  results  obtained  on  file,  which  shall 
be  accessible  to  the  administration  upon  demand. 

2.  The  drop  in  potential  in  the  rails,  measured  upon  a  length 
of  track  of  1  kilometer  taken  arbitrarily  upon  any  section  of 
the  system,  should  not  exceed  an  average  value  of  1  volt  for 
the  operating  period  of  the  normal  car  schedule. 

3.  The  feeders  tied  into  the  track  shall  be  insulated. 

4.  Where  the  tracks  contain  switches  or  crossings,    the   con- 
ductance shall  be  maintained  by  special  work. 

5.  When  the  track  crosses   a  metallic  structure,   it   should 
be  electrically  insulated,  as  much  as  possible,  throughout  the 
length  of  the  structure. 

6.  As  long  as  no  metallic  structure  is  in  the  neighborhood 
of  the  tracks,  a  drop  in  potential  greater  than  that  fixed  in 
paragraph  2  may  be  allowed,  upon  the  condition  that  no  dam- 
age  will  result,   and  particularly  no  trouble  to  telegraphic  or 
telephonic  communication,   and  none  to  railway  signals. 

7.  The  owner  of  the  distribution  system  shall  be  required 
to  make  the  installations  necessary  to  enable  the  administra- 
tion to  verify  the  fulfillment  of  the  provisions  of  this  article; 
it  should  particularly  provide,   whenever  necessary,  for  pilot 


EUROPEAN 


101 


wires   to   be  installed   between   designated   points   of   the   dis- 
tribution system. 

PROTECTION  OF  NEIGHBORING  AERIAL  LINES. 

ART.  29.  At  all  points  where  the  lines  feeding  the  traction 
system  cross  other  distribution  lines,  or  telegraph  or  telephone 
lines,  the  supports  should  be  established  with  a  view  to  protect 
mechanically  these  lines  against  contact  with  the  aerial  con- 
ductors feeding  the  traction  system. 

In  all  cases,  measures  shall  be  taken  to  prevent  the  trolley 
wire  touching  the  neighboring  lines. 

80.  England. — British  Board  of  Trade  Regulations.  Regu- 
lations made  by  the  Board  of  Trade  under  the  provisions  of  Special 
Tramways  Acts  or  Light  Railway  Orders  authorizing  "  lines  "  on 
public  roads ;  for  regulating  the  use  of  electrical  power ;  for  prevent- 
ing fusion  or  injurious  electrolytic  action  of  or  on  gas  or  water 
pipes  or  other  metallic  pipes,  structures  or  substances;  and  for 
minimising  as  far  as  is  reasonably  practicable  injurious  inter- 
ference with  the  electric  wires,  lines,  and  apparatus  of  parties 
other  than  the  Company,  and  the  currents  therein,  whether 
such  lines  do  or  do  not  use  the  earth  as  a  return. 

First  made,  March,  1894. 

Revised,  April,  1903. 

Further  revised,   August,    1904. 

Further  revised,  May,  1908. 

Further   revised,    April,    1910. 

Further  revised,   September,  1912. 

REGULATIONS. 

1.  Any  dynamo  used  as  a  generator  shall  be  of  such  pattern 
and  construction  as  to  be  capable  of  producing  a  continuous 
current  without  appreciable  pulsation. 

2.  One  of  the  two  conductors  used  for  transmitting  energy 
from  the  generator  to  the  motors  shall  be  in  every  case  insulated 
from  earth,  and  is    hereinafter  referred  to  as  the  "line";  the 
other  may  be  insulated  throughout,  or  may  be  uninsulated  in 
such  parts  and  to  such  extent  as  is  provided  in  the  following 
regulations,  and  is  hereinafter  referred  to  as  the  "return." 

The  Board  of  Trade  will  be  prepared  to  consider  the 
issue  of  regulations  for  the  use  of  alternating  currents  for 
electrical  traction  on  application. 


102  KU&QfrEA.'N   PRACTICE 

3.  Where  any  rails  on  which  cars  run  or  any  conductors 
laid  between  or  within  three  feet  of  such  rails  form  any  part 
of  a  return,  such  part  may  be  uninsulated.     All  other  returns 
or  parts  of  a  return  shall  be  insulated,  unless  of  such  sectional 
area  as   will  reduce  the  difference  of  potential  between  the 
ends  of  the  uninsulated  portion  of  the  return  below  the  limit 
laid  down  in  Regulation  7. 

4.  When  any  uninsulated  conductor  laid  between  or  within 
three  feet  of  the  rails  forms  any  part  of  a  return,  it  shall  be 
electrically  connected  to  the  rails  at  distances  apart  not  ex- 
ceeding 100  feet  by  means  of  copper  strips  having  a  sectional 
area  of  at  least  one-sixteenth  of  a  square  inch,  or  by  other  means 
of  equal  conductivity. 

5.  (a)  When  any  part  of  a  return  is  uninsulated  it  shall  be 
connected  with  the  negative  terminal  of  the  generator,  and  in 
such  case  the  negative  terminal  of  the  generator  shall  also  be 
directly  connected,     through  the  current-indicator  hereinafter 
mentioned,  to  two  separate  earth  connections  which  shall  be 
placed  not  less  than  20  yards  apart. 

(b)  The    earth    connections    referred    to    in    this    regulation 
shall   be   constructed,    laid   and   maintained,    so   as   to   secure 
electrical  contact  with  the  general  mass  of  earth,  and  so  that, 
if  possible,  an  electromotive    force,  not  exceeding  four  volts, 
shall  suffice  to  produce  a  current  of  at  least  two  amperes  from 
one  earth  connection  to  the  other  through  the  earth,  and  a 
test  shall  be  made  once  in  every  month  to  ascertain  whether 
this  requirement  is  complied  with. 

(c)  Provided  that  in  place  of  such  two  earth  connections 
the  Company  may  make  one  connection  to  a  main  for  water 
supply  of  not  less  than  three  inches  internal  diameter,  with  the 
consent  of  the  owner  thereof  and  of  the  person  supplying  the 
water,  and  provided  that  where,  from  the  nature  of  the  soil 
or  for  other  reasons,  the  Company  can  show  to  the  satisfaction 
of  the  Board  of  Trade  that  the  earth  connections  herein  specified 
cannot  be  constructed  and  maintained  without  undue  expense 
the  provisions  of  this  regulation  shall  not  apply. 

(d)  No  portion  of  either  earth  connection  shall    be    placed 
within  six  feet  of  any  pipe  except  a  main  for  water  supply 
of  not  less  than  three  inches  internal  diameter  which  is  metal- 
lically connected  to  the  earth  connections  with  the  consents 
hereinbefore  specified. 

(e)  When  the  generator  is  at  a  considerable  distance  from 


EUROPEAN   PRACTICE  103 

the  tomway  the  uninsulated  return  shall  be  connected  to  the 
negative  terminal  of  the  generator  by  means  of  one  or  more 
insulated  return  conductors,  and  the  generator  shall  have  no 
other  connection  with  earth;  and  in  such  case  the  end  of  each 
insulated  return  connected  with  the  uninsulated  return  shall 
be  connected  also  through  a  current  indicator  to  two  separate 
earth  connections,  or  with  the  necessary  consents  to  a  main 
for  water  supply,  or  with  the  like  consents  to  both  in  the  man- 
ner prescribed  in  this  regulation. 

(f)  The  current  indicator-  may  consist  of  an  indicator  at  the 
generating  station  connected  by  insulated  wires  to  the  term- 
inals of  a  resistance  interposed  between  the  return  and  the 
earth  connection  or  connections,  or  it  may  consist  of  a  suitable 
low-resistance  maximum  demand  indicator.  The  said  re- 
sistance, or  the  resistance  of  the  maximum  demand  indicator, 
shall  be  such  that  the  maximum  current  laid  down  in  Regula- 
tion 6  (I)  shall  produce  a  difference  of  potential  not  exceeding 
one  volt  between  the  terminals.  The  indicator  shall  be  so 
constructed  as  to  indicate  correctly  the  current  passing  through 
the  resistance  when  connected  to  the  terminals  by  the  insulated 
wires  before-mentioned. 

6.  When  the  return  is  partly  01  entirely  uninsulated  the  Com- 
pany shall  in  the  construction  and  maintenance  of  the  tram- 
way (a)  so  separate  the  uninsulated  return  from  the  general 
mass  of  earth,  and  from  any  pipe  in  the  vicinity;  (b)  so  con- 
nect together  the  several  lengths  of  the  rails;  (c)  adopt  such 
means  for  reducing  the  difference  produced  by  the  current  be- 
tween the  potential  of  the  uninsulated  return  at  any  one  point 
and  the  potential  of  the  uninsulated  return  at  any  other  point ; 
and  (d)  so  maintain  the  efficiency  of  the  earth  connections 
specified  in  the  preceding  regulations  as  to  fulfill  the  following 
conditions,  viz.: 

(I)  That   the  current  passing  from  the  earth  connections 
through   the   indicator   to   the   generator   or   through   the 
resistance  to  the  insulated  return  shall  not  at  any  time 
exceed   either   two   amperes   per  mile   of   single   tramway 
line    or  five  per  cent  of  the  total  current  output^of  the 
station. 

(II)  That  if  at  any  time  and  at  any  place  a  test  be  made 
by  connecting  a  galvanometer  or  other  current-indicator 
to  the  uninsulated  return  and  to  any  pipe  in  the  vicinity, 
it  shall  always  be  possible  to  reverse  the  direction  of  any 
current  indicated  by  interposing  a  battery  of  three  Le- 


104  EUROPEAN   PRACTICE 

clanche  cells  connected  in  series  if  the  direction  of  the 
current  is  from  the  return  to  the  pipe,  or  by  interposing 
one  Leclanche  cell  if  the  direction  of  the  current  is  from 
the  pipe  to  the  return. 

The  owner  of  any  such  pipe  may  require  the  Company  to 
permit  him  at  reasonable  times  and  intervals  to  ascertain  by 
test  that  the  conditions  specified  in  (II)  are  complied  with  as 
regards  his  pipe. 

7.  When  the  return  is  partly  or  entirely  uninsulated  a  con- 
tinuous record  shall  be  kept  by  the  Company  of  the  difference 
of  potential  during  the  working  of  the  tramway  between  points 
on  the  uninsulated  return.     If  at  any  time  such  difference  of 
potential  between  any  two  points  exceeds  the  limit  of  seven 
volts,   the   Company  shall  take  immediate  steps   to  reduce  it 
below  that  limit. 

8.  The  current   density  in  the  rails   shall  not   exceed  nine 
amperes  per  square  inch  of  the  cross  sectional  area. 

9.  Every   electrical   connection   with   any   pipe   shall   be   so 
arranged  as  to  admit  of  easy  examination,  and  shall  be  tested 
by  the  Company  at  least  once  in  every  three  months. 

10.  The  insulation  of  the  line  and  of  the  return  when  in- 
sulated, and  of  all  feeders  and  other  conductors,  shall  be  so 
maintained  that  the  leakage  current  shall  not  exceed  one  hun- 
dredth of  an  ampere  per  mile  of  tramway.     The  leakage  cur- 
rent shall  be  ascertained  not  less  frequently  than  once  in  every 
week  before  or  after  the  hours  of  running  when  the  line  is  fully 
charged.     If  at  any  time  it  should  be  found  that  the  leakage 
current  exceeds  one-half  of  an  ampere  per  mile  of  tramway 
the  leak  shall  be  localised  and  removed  as  soon  as  practicable, 
and  the  running  of  the  cars  shall  be  stopped  unless  the  leak 
is    localised    and    removed    within    24    hours.     Provided    that 
where  both  line  and  return  are  placed  within  a  conduit  this 
regulation  shall  not  apply. 

11.  The  insulation  resistance  of  all  continuously  insulated 
cables  used  for  lines,  for  insulated  returns,  for  feeders,  or  for 
other  purposes,  and  laid  below  the  surface  of  the  ground,  shall 
not  be  permitted  to  fall  below  the  equivalent  of  10  megohms 
for  a  length  of  one  mile.     A  test  of  the  insulation  resistance  of 
all  such  cables  shall  be  made  at  least  once  in  each  month. 

12.  Any  insulated  return  shall  be  placed  parallel  to  and  at 
a  distance  not  exceeding  three  feet  from  the  line  when  the  line 
and  return  are  both  erected  overhead,  or  eighteen  inches  when 
they   are  both  laid  underground. 


EUROPEAN   PRACTICE  105 

13.  In  the  disposition,  connections,  and  working  of  feeders, 
the  Company  shall  take  all  reasonable  precautions   to  avoid 
injurious  interference  with   any  existing  wires. 

14.  The    Company   shall    so    construct    and    maintain    their 
system  as  to  secure  good  contact  between  the  motors  and  the 
line  and  return  respectively. 

15.  The  Company  shall  adopt  the  best  means  available  to 
prevent  the  occurrence  of  undue  sparking  at  the  rubbing  or 
rolling  contacts  in  any  place  and  in  the  construction  and  use 
of  their  generator  and  motors. 

16.  Where  the  line  or  return  or  both  are  laid  in  a  conduit 
the  following  conditions  shall   be  complied   with  in  the  con- 
struction and  maintenance  of  such  conduit: 

(a)  The   conduit  shall  be  so  constructed  as  to  admit  of 
examination   of  and   access  to  the  conductors   contained 
therein   and  their  insulators   and   supports. 

(b)  It    shall  be  so  constructed  as  to  be  readily  cleared 
of  accumulation  of  dust  or  other  debris,  and  no  such  ac- 
cumulation shall  be  permitted  to  remain. 

(c)  It  shall  be  laid  to  such  falls  and  so  connected  to 
sumps  or  other  means   of  drainage,   as   to   automatically 
clear  itself  of  water  without  danger  of  the  water  reaching 
the  level  of  the  conductors. 

(d)  If    the   conduit   is   formed   of   metal,    all   separate 
lengths  shall  be  so  jointed  as  to  secure  efficient  metallic 
continuity   for   the   passage   of   electric   currents.     Where 
the  rails  are  used  to  form  any  part  of  the  return  they  shall 
be  electrically  connected  to  the  conduit  by  means  of  copper 
strips  having  a  sectional  area  of  at  least  one-sixteenth  of 
a  square  inch,   or  other  means  of  equal  conductivity,   at 
distances  apart  not  exceeding  100  feet.     Where  the  return 
is  wholly  insulated  and  contained  within  the  conduit.,  the 
latter  shall  be  connected  to  earth  at  the  generating  station 
or    sub-station    through    a    high    resistance  galvanometer 
suitable  for  the  indication  of  any  contact  or  partial  contact 
of  either  the  line  or  the  return  with  the  conduit. 

(e)  If  the  conduit  is  formed  of  any  non-metallic  material 
not  being  of  high  insulating  quality   and  impervious  to 
moisture  throughout,  the  conductors  shall  be  carried  on 
insulators  the  supports  for  which  shall  be  in  metallic  con- 
tact with  one  another  throughout. 

(f )  The  negative  conductor  shall  be  connected  with  earth 
at  the  station  by  a  voltmeter  and  may  also  be  connected 
with  earth  at  the  generating  station  or  sub-station  by  an 
adjustable  resistance  and  current-indicator.     Neither  con- 
ductor shall  otherwise  be  permanently  connected  with  earth. 

(g)  The  conductors  shall  be  constructed  in    sections   not 
exceeding  one-half  a  mile  in  length,  and  in  the  event  of  a 


106  EUROPEAN   PRACTICE 

leak  occurring  on  either  conductor  that  conductor  shall 
at  once  be  connected  with  the  negative  pole  of  the  dynamo, 
and  shall  remain  so  connected  until  the  leak  can  be  re- 
moved. 

(h)  The  leakage  current  shall  be  ascertained  daily,  be- 
fore or  after  the  hours  of  running,  when  the  line  is  fully 
charged,  and  if  at  any  time  it  shall  be  found  to  exceed 
one  ampere  per  mile  of  tramway  the  leak  shall  be  localised 
and  removed  as  soon  as  practicable,  and  the  running  of 
the  cars^  shall  be  stopped  unless  the  leak  is  localised  and 
removed  within  24  hours. 

17.  The  Company  shall,  so  far  as  may  be  applicable  to  their 
system  of  working,  keep  records  as  specified  below.  These 
records  shall,  if  and  when  required,  be  forwarded  for  the  in- 
formation of  the  Board  of  Trade. 

Number  of  cars  running. 

Number  of  miles  of  single  tramway  line. 

DAILY  RECORDS. 

Maximum  working  current. 

Maximum  working  pressure. 

Maximum  current  from  the  earth  plates  or  water-pipe  con- 
nections (vide  Regulation  6  (I))  where  the  indicator  is  at  the 
generating  works. 

Fall  of  potential  in  return  (vide  Regulation  7). 

Leakage  current    (vide  Regulation    16   (h)). 

WEEKLY  RECORDS. 

Leakage  current   (vide  Regulation  10). 

Maximum  current  from  the  earth  plates  or  water-pipe  con- 
nections (vide  Regulations  6  (I))  where  a  maximum  demand 
indicator  is  used. 

MONTHLY  RECORDS. 

Condition  of  earth  connections   (vide  Regulation  5). 
Minimum  insulation  resistance  of  insulated   cables  in  meg- 
ohms per  mile  (vide  Regulation  11). 

QUARTERLY  RECORDS. 
Conductance  of  connections  to  pipes  (vide  Regulation  9). 

OCCASIONAL  RECORDS. 

Specimens  of  tests  made  under  provisions  of  Regulation  6  (II.) 
Board  of  Trade, 

7,  Whitehall  Gardens,  S.  W. 
September,  1912. 


EUROPEAN   PRACTICE  107 

81.  Spain— Electric  Legislation.     Law  of  March  23,  1900. 

ARTICLE  50.  To  prevent  the  return  current  of  electric  tram- 
way lines  from  exercising  any  electrolytic  effects,  the  following 
measures  shall  be  taken: 

(1)  The  rails  of  each  one  of  the  tracks  are  bonded  by  welding 
or  by  connections  formed  of  short  copper  cables,  or  of  equiva- 
lent cables  made  of  some  other  metal,  the  section  of  which 
having  to  exceed  100   square  millimeters   per  track,  and  shall 
be  made  as  large  as  possible. 

(2)  At  intervals  of  100  meters,  or  at  shorter  distances,  the 
tracks  shall  be  cross-bonded. 

(3)  In  case  the  official  inspector  should  deem  it  necessary, 
a  cable  will  have  to  be  stretched  in  every  line,  which  will  have 
to  be  intimately  connected  with  both  tracks;  and 

(4)  The  dimensions  of  all  cables  and  wires  constituting  such 
system  will  have  to  be  calculated  upon  a  basis  that  the  potential 
difference  between  the  generator  terminals  and  the  point  of 
the  tracks  remotest  from  them  will  not  exceed  an  amount  of 
seven  volts. 

H.     SUMMARY  OF  EUROPEAN  CONDITIONS. 

Conditions  in  Germany,  Italy,  France  and  England  as  Reported 
to  the  Visiting  Committee  by  Various  Authorities  in 
these  Countries. 

82.  Present  Electrolysis  Conditions. 

Germany.  Considerable  damage  was  found  in  many  cities 
prior  to  the  application  of  the  Earth  Current  Commission's 
Regulations;  in  one  case  service  pipe  trouble  occurred  as  often 
as  once  a  month.  Generally,  however,  extensive  damage  was 
not  known  until  it  was  revealed  by  investigation;  thus,  many 
of  the  cities  which  were  surveyed  by  the  Commission,  and 
where  more  or  less  corrosion  was  found,  had  previously  reported 
no  damage. 

In  general,  the  pipe  owning  interests  stated  that  the  situa- 
tion was  such  that  the  work  of  the  Earth  Current  Commission 
was  urgently  needed.  Some  railway  engineers  held  that  a 
considerable  amount  of  corrosion  ascribed  to  stray  railway 
current  was  in  fact  due  to  other  sources,  or  to  self -corrosion. 

Many   very   thorough   tests   have   been   made  in   Germany, 


108  EUROPEAN   PRACTICE 

and  a  large  majority  of  these  have  shown  that  corrosion  was 
being  produced  by  stray  railway  currents. 

The  more  prosperous  companies  and  municipalities  spent 
money  for  improvements  after  the  publication  of  the  Regula- 
tions of  the  Earth  Current  Commission.  Exact  information 
was  not  available  regarding  the  number  of  places  where  changes 
had  been  made,  but  the  best*  information  indicated  that  the 
number  was  between  20  and  30.  Of  these,  about  100,000  marks 
each  was  spent  in  Danzig,  Strassburg  and  Erfurt,  re-arranging 
the  resistances  in  existing  return  conductors,  and  Dresden 
was  engaged  in  insulating  the  existing  bare  conductors,  and 
generally,  the  most  important  cities  were  rapidly  improving 
their  return  circuit  conditions. 

The  present  conditions  in  Germany  are  considered  satis- 
factory where  the  electric  railways  have  conformed  to  the 
Commission  Regulations,  or  where  conditions  were  already 
equally  good;  in  other  cases  the  conditions  are  considered 
to  be  unsatisfactory.  No  cases  of  extensive  damage  to  cable 
sheaths  were  found. 

Italy.  Very  little  damage,  if  any,  is  known  in  Italy,  and  the 
conditions  are  said  to  be  satisfactory.  This  favorable  report 
is  based  on  the  absence  of  complaints. 

France.  Outside  of  Paris,  there  is  little  damage  caused  by 
tramway  systems,  which  generally  observe  a  one  volt  per 
kilometer  rail  drop  limit,  contained  in  regulations  issued  by 
the  Ministry  of  Public  Works.  No  adequate  or  complete  tests 
have  been  made  in  France,  although  some  testing  has  been 
done  in  Paris  following  the  development  of  trouble. 

In  Paris,  60  to  70  cases  of  damage  to  pipes  have  been  found 
in  a  year,  and  the  actual  minimum  cost  of  repairs  was  esti- 
mated to  be  60,000  francs;  however,  it  was  held  that  the  para- 
mount consideration  was  the  danger  to  security  of  service,  since 
nearly  all  cases  caused  losses  in  buildings,  although  there  were 
no  explosions. 

At  least  30  to  35  per  cent  of  the  total  number  of  cases  re- 
ported were  due  to  re-arrangement  of  the  Edison  two-wire  and 
three-wire  mains;  such  troubles  are  local  and  temporary,  while 
in  other  cases  the  troubles  are  persistent. 

A  very  considerable  amount  of  damage  in  Paris  is  due  to 
the  "  Metropolitan"  subway  system,  which  claims  exemption 
from  the  one-volt  per  km.  rule,  not  being  a  tramway  system. 
With  this  exception,  conditions  in  France  are  said  to  be  gen- 
erally satisfactory. 


EUROPEAN   PRACTICE  .         109 

England.  Considerable  damage  is  said  to  have  occurred  in 
the  early  days  of  electric  traction  in  England,  although  such 
damage  was  apparently  insignificant  compared  to  conditions 
familiar  in  America.  Practically  no  damage  has  occurred  in 
recent  yeais,  and  certainly  no  extensive  damage.  Two  or 
three  cases,  local  in  character  and  of  small  extent,  have  occurred 
in  localities  where  the  Board  of  Trade  regulations  were  complied 
with. 

In  England  there  is  very  little  good  evidence  in  the  way  of 
tests,  and  the  general  statements  of  immunity  are  based  on 
the  absence  of  trouble.  The  Post  Office  and  the  South  Metro- 
politan Gas  Company  (London)  both  make  systematic  tests 
and  find  no  trouble,  with  the  exception  that  the  Post  Office 
has  from  time  to  time  encountered  difficulties  due  to  stray 
currents,  which  were  however  generally  quite  local  in  character. 

While  it  is  generally  stated  in  England  that  there  is  little 
actual  damage  to  piping  systems,  and  that  the  problem  is  not 
an  important  issue  with  the  owners  of  gas  piping  systems,  there 
is  considerable  feeling  among  the  privately  owned  gas  com- 
panies that  they  are  not  adequately  protected  by  the  Board 
of  Trade  Regulations,  since  they  cannot  recover  damages  in 
case  corrosion  occurs  where  the  Regulations  are  complied  with. 
This  has  led  to  numerous  applications  to  Parliament  for  special 
clauses  in  Acts  granting  powers  to  electric  railway  undertak- 
ings; most  of  these  have  been  refused,  but  some  have  been 
granted. 

It  is  generally  admitted  that  the  Board  of  Trade  Regulations, 
as  originally  drawn,  were  empirical,  and  that  they  might  be 
remodelled  with  advantage,  but  .since  the  only  feature  of  the 
regulations  actually  rigidly  enforced :  namely,  the  limit  for  over- 
all rail  drop,  results  in  substantial  immunity,  the  great  dif- 
ficulty attending  revision  does  not  seem  justified. 

83.  Protective  Measures  in  Vogue. 

FEEDERS. 

Germany.  Insulated  return  feeders  are  used  almost  uni- 
versally in  Germany.  In  Berlin  and  Hamburg  these  return 
feeders  are  of  the  same  number  and  size  as  the  positive  feeders, 
but  generally  in  other  towns  the  return  feeders  are  of  smaller 
cross-section.  Separate  feeders  are  generally  used,  but  not 
exclusively,  as  feeders  with  resistance  taps  are  used  in  some 


110  EUROPEAN   PRACTICE 

cases.  Formerly  there  were  cases  of  feeders  tapping  at  several 
points,  but  important  cases  have  been  corrected  by  the  inser- 
tion of  resistances.  (The  distinction  between  copper  which 
merely  parallels  the  rails,  and  feeders  intended  to  maintain 
equi-potential  points  in  the  rail  net-work,  is  clearly  understood 
in  Germany). 

Negative  boosters  are  used  in  several  cases,  but  the  general 
practice  is  not  to  use  them.  The  tramway  in  Danzig,  operated 
by  a  private  company,  and  having  a  maximum  load  of  600 
kw.,  has  used  boosters  since  1906. 

Return  feeder  systems  are  carefully  calculated  in  recent  in- 
stallations; the  same  grade  of  insulation  is  generally  provided 
for  both  positive  and  negative  feeders.  No  design  data  for 
feeder  resistances  were  obtained. 

England.  Insulated  return  feeders  are  used  in  England, 
wherever  return  feeders  are  necessary  to  bring  the  rail  drop 
within  the  B.O.T.  regulations  Separate  feeders  are  generally 
used.  (As  in  Germany,  the  feeders  are  intended  to  maintain 
the  rail  taps  at  the  same  potential  throughout  the  system). 

Negative  boosters  are  more  extensively  used  than  in  Germany. 
They  are  very  commonly  used  in  the  larger  systems,  although  in 
one  large  city  their  use  was  abandoned  after  they  had  been  in 
operation  for  some  time.  They  are  considered  more  economical 
than  resistances  in  the  return  feeders,  and  also  to  provide  better 
regulation  where  the  load  centers  shift. 

Return  feeder  systems  are  only  calculated  in  the  larger,well 
supervised  systems,  elsewhere  they  are  installed  on  "cut-and- 
try"  methods.  The  same  grade  of  insulation  is  usually  provided 
for  both  positive  and  negative  feeders. 

Italy.  Return  feeders  are  not  iised  for  tramways  in  Italy. 

France.  Insulated  return  feeders  are  used  for  the  conduit 
tramways  in  Paris,  but  little  elsewhere.  Most  systems  have 
but  one  feeding  point  to  the  rails.  Boosters  are  very  little 
used,  the  only  system  found  to  be  equipped  with  boosters  was 
that  of  the  Cie.  des  Tramways  de  Paris  et  du  Dept.  de  la  Seine. 

VOLTAGE  AND  CURRENT  CONDITIONS. 

Germany.  Where  return  circuits  have  not  been  remodelled 
in  accordance  with  the  Commission  Regulations,  overall  volt- 


EUROPEAN   PRACTICE  111 

age  limits  vary  greatly,  but  in  the  majority  of  cases  they  are 
between  5  and  10  volts.  Other  systems  will  be  from  2  to  5 
volts.  Negative  feeders  are  designed  for  equal  drop. 

England.  Overall  rail  drops  for  tramways  in  England  are 
generally  very  much  lower  than  the  B.O.T.  requirement,  averag 
ing  probably  2.5  to  3  volts,  with  the  exception  of  occasional 
drops,  which  may  be  as 'high  as  15  or  20  volts,  due  to  extra- 
ordinary traffic  at  foot-ball  matches,  etc.  The  railways  prob- 
ably have  higher  overall  voltages  than  the  tramways.  Glasgow, 
which  voluntarily  adopted  a  2  volt  rail  drop  limit,  Manchester, 
and  other  large  towns,  have  extraordinarily  low  rail  drops. 
Electrolysis  conditions  throughout  the  United  Kingdom  are 
generally  said  to  be  satisfactory,  although  some  private  gas 
companies  do  not  agree  to  this.  Potential  differences  between 
pipes  and  rails  are  said  to  be  generally  less  than  1  volt. 

Negative  feeders  are  designed  for  equal  drop. 

France.  It  is  stated  that  the  tramways  in  France  generally 
endeavor  to  observe  the  1  volt  per  km.  limit.  Potential  dif- 
ferences between  pipes  and  rails  rarely  exceed  1  volt  (However 
we  observed  a  6  volt  potential  in  Paris). 

MISCELLANEOUS    PROTECTIVE    MEASURES. 

Drainage  System.  Electrical  drainage  was  formerly  applied 
in  one  or  two  cases  in  Germany,  notably  in  Aachen,  but  it  was 
abandoned  on  account  of  damage  produced  by  it,  first,  due  to 
joint  corrosion,  and  second,  damage  to  other  underground 
structures.  It  is  condemned  by  the  engineers  of  the  Earth 
Current  Commission. 

Electrical  drainage  is  not  employed  in  Italy  or  France. 

In  England,  it  is  not  approved  as  a  general  measure  to  afford 
relief  from  stray  current,  although  there  are  a  few  special  in- 
stances of  its  application  to  the  Railway  Company's  own  lead 
covered  cables,  where  the  common  practice  is  to  bond  to  the 
rails  at  many  points.  One  engineer  thought  that  it  might  be 
applied  where  currents  were  small,  except  to  gas  pipes  on  account 
of  the  danger  from  sparking,  he  also  thought  that  it  would  be 
undesirable  in  America  where  large  currents  are  carried. 

Negative  Trolley  or  Periodic  Reversal.  The  trolley  wire  was 
originally  made  negative  in  Nurnberg,  and  in  St.  Gall,  Switzer- 


112  EUROPEAN   PRACTICE 

land,    but   not    periodically   reversed.     The   scheme   has   been 
abandoned  in  both  places. 

This  connection  has  not  been  used  for  tramways  in  Italy, 
France  or  England. 

Three-Wire  System.  The  three  wire  system  has  been 
applied  to  electric  railways  in  a  few  cases  in  Germany.  In 
each  case  the  distribution  of  load  between  polarities  was  by 
districts,  that  is,  certain  entire  sections  will  have  the  trolley 
wire  positive,  and  others  will  have  the  trolley  wire  negative. 
Under  these  conditions  the  systems  may  become  considerably 
unbalanced. 

In  France,  the  Nord-Sud  Chemin  de  Fer  employs  a  three- 
wi^re  system  with  two  motors  per  car,  positive  and  negative, 
the  running  rails  acting  as  a  grounded  neutral. 

In  England  the  three-wire  system  has  not  been  applied  to 
tramways.  The  City  and  South  London  Underground  Rail- 
way employs  it,  but  this  will  be  discontinued  following  con- 
solidation with  other  systems. 

Average  Feeding  Distances.  In  England,  the  average  feed- 
ing distances  are  said  to  be  from  2  to  3  miles. 

Joints  in  Cast-iron  Mains.  Cast-iron  pipes  in  England  and 
Germany  are  generally  of  the  lead  calked  bell  and  spigot  type. 
In  Germany  flanged  joints  are  frequently  used  for  special 
fittings,  valves,  T's  and  hydrant  taps  for  water  mains.  Cast- 
iron  pipes  are  little  used  in  France;  pipe  joints  are  either  lead 
calked  bell  and  spigot,  or  in  large  pipes  flanged  with  rubber 
gaskets.  Insulating  joints  are  not  used,  except  that  in  England 
it  is  said  that  they  are  occasionally  used  for  water  pipes  in 
very  special  cases. 

Insulating  Coverings.  In  Germany  it  is  held  that  insulating 
coverings  do  not  afford  protection  against  electrolysis,  as  their 
effect  is  merely  to  concentrate  escaping  stray  currents,  since 
perfect  coverings  cannot  be  maintained.  They  should  only  be 
used  where  protection  against  chemical  corrosion  is  desired, 
due  to  the  character  of  the  soil. 

In  France,  gas  engineers  stated  that  insulating  coverings  were 
being  studied,  but  it  was  not  believed  that  they  would  prove 
practicable. 


EUROPEAN   PRACTICE  113 

In  England,  insulating  coverings  are  not  considered  good 
protection  against  stray  railway  currents.  High  pressure  gas 
pipes  have  been  covered  with  pitch  canvas,  and  the  London 
Water  Board  pipes  are  provided  with  an  asphalt  dip  coating, 
but  more  as  protection  against  chemical  corrosion. 

Insulating  Joints  in  Telephone  Cables.  Not  used  in  Ger- 
many or  England. 

Double  Trolley.  The  double  trolley  system  is  not  in  general 
use  in  any  of  the  countries  visited.  One  or  two  very  special 
cases  near  Laboratories  in  Germany,  the  district  within  2  or 
3  miles  of  the  Greenwich  Observatory,  and  some  conduit  tram- 
ways of  the  London  County  Council  System,  were  the  only 
cases  noted.  The  double  trolley  is  also  used  in  connection 
with  a  few  miles  of  rail -less  trolley  in  England. 

Corrosive  Effects  of  Soil.  In  Germany  the  possibility  of 
chemical  corrosion  (that  is,  corrosion  without  an  external 
supply  of  electricity)  is  recognized,  and  distinction  is  made 
between  such  corrosion  and  that  produced  by  stray  currents. 
Pipe  corrosion  has  actually  been  found  under  conditions  where 
it  could  not  have  been  produced  by  stray  currents.  The  re- 
sistance of  soil  is  said  to  vary  from  1  ohm  to  2000  ohms  per 
cubic  meter,  averaging  about  100  ohms  per  cubic  meter. 

No  definite  information  was  obtained  in  England  regarding 
the  corrosive  properties  of  soil,  but  it  was  stated  that  chemical 
corrosion  was  known  to  occur.  Such  corrosion  does  not, 
however,  produce  acute  conditions,  as  in  electrolysis;  it  is  more 
like  ordinary  oxidation. 

Effect  of  Roadbed  Construction  on  Leakage  Current.     The 

authorities  consulted  in  Germany  were  of  the  opinion  that  the 
road-bed  constructions  used  did  not  effect  a  reduction  of  leak- 
age from  the  tracks.  A  similar  opinion  was  held  in  England. 
(See  Fig.  10-13). 

Rail-Weights.  In  Germany  the  common  rail  weights  are 
50-60  Kg.  per  meter  for  tramways,  and  30-40  Kg.  per  meter 
for  interurban  lines.  In  France  the  ordinary  rail-weights  are 
46  to  51  Kg.  per  meter.  In  England  rail-weights  vary  from 
70  to  100  Ibs.  per  yard,  in  the  majority  of  cases.  (See  Fig.  14). 


114  EUROPEAN   PRACTICE 

Welded  Rail- Joints.  In  Germany  Thermit  welds  are  used 
to  some  extent,  they  are  becoming  more  common.  In  France 
the  rails  of  the  System  Cie.  de  Omnibus  Thomson-Houston, 
are  welded. 

In  England  Thermit  welds  have  been  very  extensively  used, 
giving  good  results  electrically,  but  having  short  life  due  to 
mechanical  weakness  where  traffic  is  heavy.  A  type  of  elec- 
trically welded  continuous  rail,  very  extensively  used  in  Leeds, 
and  to  an  increasing  extent  in  Manchester  and  Glasgow,  is 
giving  excellent  results,  being  mechanically  strong  and  pro- 
viding good  electrical  conductivity. 

Rail-bonds.  Solid  copper  pin  type  bonds,  usually  1  meter 
long,  are  most  commonly  used  in  Germany,  and  also  in  France. 
The  Metropolitan  System  in  Paris  places  the  bonds  under  the 
base  flange  of  the  rail. 

In  England,  solid  copper  pin  type  bonds,  protected  bonds 
inside  of  fish  plates,  and  other  types  familiar  in  America,  are 
generally  used.  (See  Fig.  15). 

Cross-bonds.  In  Germany,  cross-bonds  are  used  about  every 
10  rails,  i.e.,  every  100  meters.  In  France,  cross-bonds  are 
placed  every  50-100  meters,  they  have  the  same  area  as  the 
rail-bonds.  In  England  cross-bonds  are  placed  generally 
every  40  yards,  they  have  the  same  area  as  the  rail-bonds. 
(See  Fig.  16). 

Depth  of  Pipes  etc.  Below  Surface.  In  Germany,  gas  pipes 
are  generally  laid  0.8-1.  meter,  and  water  pipes  1-1.5  meters, 
below  the  surface.  In  France,  gas  pipes  are  laid  where  pos- 
sible 0.6  meter  below  the  surface,  L.T.  cables  0.7  meter,  and 
H.T.  cables  1.3  meters.  In  England  1  foot  is  said  to  be  danger- 
ous; 2  feet  was  given  by  one  authority  as  an  average  and  2.5 
to  5  feet  by  another.  In  all  cases  the  above  depths  are  only 
typical,  the  practice  varies  widely. 

Mains  on  Both  Sides  of  Streets.  In  Germany,  France  and 
England,  mains  are  laid  on  both  sides  of  principal  streets,  or 
streets  wider  than  14  meters  (Paris)  or  in  streets  with  wood 
or  asphalt  pavements,  and  generally  in  the  larger  towns.  In 
narrow  streets  or  in  unimportant  places,  one  main  is  used. 


EUROPEAN   PRACTICE      «  115 

84.  Economic  Aspects  of  the  Electrolysis  Problem.      About 
40   per    cent    of    the    electric    railway    systems    in    Germany, 
and  about  70  per  cent  in  England,    are  municipally  owned. 
In  Germany  one  authority  thought  that  municipalities  were 
more  ready  than  private  companies  to  spend  money  for  the 
purpose  of  improving  their  return  circuits,  'but  in  England  it 
was  thought  that  there  was  no  difference  in  this  respect. 

Opinions  differed  in  Germany  as  to  whether  or  not  the  pre- 
vailing regulations  constituted  a  financial  hardship.  In  England, 
the  Board  of  Trade  regulations  are  nowhere  considered  a  hard- 
ship, and  when  inquiry  was  made  as  to  whether  the  existing 
regulations  had  retarded  the  development  of  electric  railways, 
the  authorities  consulted  uniformly  stated  that  this  was  not 
the  case.  It  appears  that  in  fact  a  saturation  point  has  been 
reached,  and  busses  are  being  used  where  tramways  would  not 
pay.  Traffic  conditions  are  said  to  be  quite  as  heavy  in  Eng- 
land as  in  the  United  States.  Only  one  authority  in  England 
ventured  an  estimate  of  the  average  load  factor  for  English 
electric  railway  systems,  he  estimated  it  to  be  35  per  cent. 

There  is  very  little  overhead  feeder  line  construction  in 
Germany,  and  almost  none  in  England. 

85.  Regulations    and    Tests.     The    German    Earth    Current 
Commission   Regulations   only  attain  the  force  of  law  when 
incorporated   in   the   contracts   between   civil   authorities   and 
the  railroad  companies,  or,  as  in  the  case  of  many  cities,  where 
it  is  provided  that  new  work  be  done  in  accordance  with  "exist- 
ing   technical    standards."     The    Commission   regulations    are 
being  generally  incorporated  in  contracts  for  new  enterprises 
or   extensions.     Also,    other   undertakings   not   subject   to   its 
provisions  are  changing  over  voluntarily  for  reasons  of  policy 
or  economy,  or  as  the  result  of  compromise  to  avoid  litigation; 
this  is  said  to  be  the  case  in  30  or  40  important  towns. 

So  far  as  could  be  ascertained,  no  local  ordinances  exist  in 
Germany  regarding  electrolysis.  In  England,  there  are  no 
local  ordinances  which  have  the  effect  of  modifying  the  Board 
of  Trade  regulations.  Certain  gas  companies  have  obtained 
special  statutory  oiders,  fixing  the  responsibility  for  damage, 
but  these  do  not  modify  the  Board  of  Trade  regulations. 

In  applying  the  Earth  Current  Commission  Regulations  in 
Germany,  the  term  "average  schedule  traffic"  is  interpreted 
to  mean  the  average  for  the  entire  period  of  operation  which 


116  .       EUROPEAN   PRACTICE 

is  usually  18  or  19  hours  per  day.  If  the  measurements  are 
not  actually  taken  over  the  entire  period,  they  are  corrected 
to  obtain  a  figure  corresponding  to  this  average. 

In  England,  measurements  are  based  on  an  average  for 
about  20  minutes  at  peak  load.  The  "average"  is  obtained 
as  the  mean'  between  the  average  of  the  maxima  during  this 
period,  disregarding  unusually  high  swings,  and  the  actual 
aveiage  of  all  measurements.  This  quantity  is  usually  obtained 
in  practice  from  inspection  of  recording  instrument  charts. 

The  British  Board  of  Trade  makes  inspections  on  its  own 
initiative,  because  it  is  responsible  for  its  rules,  which  have 
substantially  the  force  of  law;  they  also  investigate  complaints. 
There  are  no  regular  inspections,  on  account  of  the  lack  of  a 
proper  appropriation;  most  of  its  information  is  obtained  by 
means  of  circular  returns,  provided  for  in  the  Regulations. 
The  latest  call  for  a  return  was  issued  in  1906. 

In  Germany,  permanent  means  for  measuring  overall  poten- 
tials are  very  generally  provided,  but  the  methods  of  doing 
this  vary  widely.  Pilot  wires  are  usually  provided  for  new 
installations  in  France. 

In  England,  pilot  wires  are  universally  used  in  connection 
with  recording  instruments.  The  practice  varies  widely,  but 
the  most  common  method  employs  14  or  16  gauge  wires  laid 
with  the  main  cables,  and  extended  beyond  them. 

Bond  testing  is  generally  done  in  Germany  on  some  syste- 
matic basis,  more  often  annually,  but  in  some  large  systems 
semi-annually.  The  bond  testing  devices  are  generally  of  the 
three  contact  type  with  differential  galvanometer.  Some  of 
these  are  said  to  be  undesirable  on  account  of  the  form  of  the 
contact,  others  because  the  rail  joint  points  span  too  short 
a  length,  or  on  account  of  the  type  of  galvanometer  employed, 
etc.  In  England,  it  is  stated  that  there  is  practically  no  .sys- 
tematic bond  testing  except  in  the  large,  well  supervised  systems. 

I.     GENERAL  REMARKS. 

86.  Germany.  Where  municipalities  own  the  water,  gas  and 
street  railway  systems,  they  may  prefer  to  assume  the  cost  of 
damage  rather  than  making  larger  expenditure  for  protection 
of  their  pipes.  There  are  cases  in  dispute  pending  in  Essen 
and  Aachen.  In  Aachen  the  drainage  system  was  formerly  used, 
but  gave  trouble;  changes  are  under  study  or  under  way. 


EUROPEAN   PRACTICE 


117 


Recently  the  case  of  Mansfeld  was  decided  against  the 
gas  company  as  the  railway  existed  before  the  gas  plant. 

Hamburg,  prior  to  the  forming  of  the  commission,  installed 
return  insulated  feeders  which  gave  valuable  information  in 
guiding  the  recommendations  of  the  commission. 

Strassburg  found  in  summer  50  %  greater  leakage  than  in 
winter  when  measurements  were  made  in  cold  weather  and 
the  ground  frozen.  In  snow  storms,  however,  the  leakage  was 
increased  as  the  cars  were  using  more  current. 

The  Prussian  Law  protects  railway  companies  against 
suits  for  damages  caused  by  stray  currents  whenever  the  pipe 
owning  concerns  did  not  apply  for  protection  against  these 
possible  damages  before  the  original  franchise  to  the  Railway 
Company  was  granted. 

Similar  laws  apply  in  other   States. 

When  the  municipality  assumes  the  operation  of  a  railway 
it  does  not  assume  responsibility  to  protect  the  pipe  owning 
companies  against  damages  due  to  stray  currents. 

87.  France.     In  Paris  pipes  for  water  are  located  in  sewers 
and  therefore  remote  from  trouble. 

Telephone  cable  troubles  are  few  in  Paris.  In  the  suburbs 
all  underground  pipe  systems  are  more  or  less  affected. 

Twenty  suits  are  now  in  litigation  between  the  gas  companies 
and  the  railways. 

J.  STATISTICAL— OPERATING— STRUCTURAL  AND 
TECHNICAL  DATA. 

TABLE  1. 

88.  Magnitude  of  Electric  Railway  Undertakings  in  German 

Empire  and  United  Kingdom. 


- 

German  Empire 
1911 

United  Kingdom 
1912 

Number   of   undertakings  
Miles  of  single  track 

258 
4  920 

262 
4  202 

No.  of  cars  of  all  kinds.    . 

26  078 

12  860 

Capital  expended  £  

54  354  625 

77  087  944 

Car  miles.    . 

430  512  031 

326  688  674 

No.  of  passengers 

2  631  892  678 

3  145  805  137 

Gross  income  £.  .  .  . 

13  237  024 

14  593  052 

118 


EUROPEAN   PRACTICE 


TABLE  2. 
89.  Tramways  not  Operated  by  Electricity. 


Miles  of  single  track. 

Horse 

Steam 

Cable 

Petrol 

locomotive 

motors,  etc. 

German  Empire,  1911 

45  1 

49  8 

4   1 

10  0 

United  Kingdom.  1912  

38.7 

42.3 

50.1 

4.8 

TABLE  3. 

90.  Ownership  of  Electric  Railway  Undertakings 
A — German  Empire,  1911. 


Private 
corporations 

Local 
authorities 

Public    ownership 
operated 
by  private 
corporations 

112 
2,711 
16,390 
32,685,120 
260,729,075 
1,519,571,662 
8.095,757 

110 
1,646 
7,756 
16,232,025 
134,466,975 
899,127,262 
4,118,873 

36 
563 
1,932 
5.437,480 
35,315,981 
213,193.754 
1,022.394 

Miles  of  single  track  

No.  of  cars  of  all  kinds  
Capital  expended  £ 

Car  miles 

No.  of  passengers 

Gross  income  £ 

B—  United  Kingdom,  1912. 

Private  corporations 

Local  authorities 

No.  of  undertakings  

91 
1,115 
3,444 

22,648,596 
81,191,368 
621,546,806 
3,534.873 

168 
3,078 
9,416 
54,439,348 
245,497,306 
2,524,358,331 
11,058,179 

Miles  of  single,  track  

No.  of  cars  of  all  kinds  

Car  miles 

No   of  passengers 

Gross  income  £                

EUROPEAN   PRACTICE 


119 


TABLE  4. 
91.  Statistics  of  Tramways  in  Large  Cities. 

A — German  Empire. 


Max.  load  kw. 

Avg.  car  miles 

Avg.  pass. 

Annual  gross 

per  diem 

per  diem 

Income-marks 

Per 

Per 

Per 

10,000 

10,000 

10.000 

Per 

Actual 

Popul. 

Actual 

Popul. 

Actual 

Popul. 

Actual 

capita. 

Hamburg 

(935,000) 

91,450 

981 

460,000 

4940 

12,208,781 

12.97 

Leipzig 

C590.000) 

2,145 

36.5 

59,910 

1020 

328,500 

(5590 

11,129,573 

18.95 

Dresden 

(550,000) 

3,300 

60.3 

59,410 

1085 

345,800 

6320 

12,324,054 

22.55 

Dusseldorf 

(360,000) 

1,386 

38.8 

27,040 

756 

183,000 

5120 

5,524,714 

15.45 

Nurnbeig 

(330,000) 

880 

26.5 

18,860 

569 

108,600 

3280 

3,543,810 

10.69 

AVERAGE  

40.5 

882 

5050 

/ 

M16.  12 

....    | 

$  3.85 

B  —  United  Kingdom. 

Max.  load  kw. 

Avg.  car  miles 

Avg.  pass. 

Annual  gross 

per  diem 

per  diem 

Income-pounds 

Per 

Per 

Per 

10,000 

10,000 

10.000 

Per 

Actual 

Popul. 

Actual 

Popul. 

Actual 

Popul. 

Actual 

capita. 

Manchester 

1,250,000) 

11.000 

88 

51,400 

411 

510,400 

4082 

887,647 

0.710 

Glasgow 

'     (1,150,000) 

11,500 

100. 

63,950 

556 

854.000 

7422 

1,070,175 

0.932 

Birmingham 

(900,000) 

36,000 

400 

368.000 

4088 

581,566 

0.616 

Leeds 

(450,000) 

4,500 

100. 

24,100 

536 

245.800 

5460 

411,531 

0.914 

Dublin 

(390.000) 

4,500 

115.4 

19,650 

504 

147,700 

3790 

293.748 

0.752 

AVERAGE  

—77— 

100.9 

.... 

481 

'4968 

....       f 

£0.791 

\ 

$     3.84 

120 


EUROPEAN   PRACTICE 


TABLE   5. 

92.  Statistics  of  Tramways  in  Small  Cities. 
A — German  Empire. 




Max.  load  kw. 

Avg.  car  miles 

Avg.  pass. 

Annual  gross 

per  diem 

per  diem 

Income-marks 

Per 

Per 

Per 

10,000 

10,000 

10,000 

Per 

Actual 

Popul. 

Actual 

Popul. 

Actual 

Popul. 

Actual 

capita. 

Casse! 
(153,078) 

469 

30.6 

6215 

406 

38,550 

251G 

1,474,199 

9.62 

Braunschweig 

(143,534) 

466 

32.5 

7090 

494 

33,100 

2306 

1,205,577 

8.40 

Erfurt 

(111,461) 

30  1 

27.3 

3580 

321 

19,010 

1708 

637,792 

5  72 

Freiburg 

(83,328) 

165 

19  8 

2742 

329 

18,860 

2264 

664,625 

7.98 

Solingen 

(50,540) 

250 

49.5 

3730 

738 

23,250 

4600 

973,240 

19.25 

AVERAGE  

32.0 

458 

.... 

2679 

....   r 

M10.20 

l 

$     2.15 

B  —  United  Kingdom. 

Max.  load  kw. 

Avg.  car  miles 

Avg.  pass. 

Annual  gross 

per  diem 

per  diem 

Income-pounds 

Per 

Per 

Per 

10,000 

10,000 

10,000 

Per 

Actual 

Popul. 

Actual 

Popul. 

Actual 

Popul. 

Actual 

capita. 

Brighton  H. 

(173,000) 

095 

57.5 

3165 

183 

31,000 

1792 

53,748 

0.311 

Dundee 

(168,600) 

1700 

101.0 

3725 

221 

48,550 

2880 

65,045 

0.386 

Preston 

(121,000) 

600 

49.6 

2660 

220 

26,200 

2166 

43,270 

0  .  358 

Coventry 

(91,000) 

750 

77.0 

2720 

299 

20,900 

2297 

39,153 

C.430 

Burton  T. 

(50,000) 

375 

74.4 

1240 

246 

9140 

1815 

16,897 

0.316 

AVERAGE  

72.0 

.... 

234 

2190 

....      / 

£     0.360 

i 

$     1  75 

EUROPEAN   PRACTICE 


121 


TABLE  6. 
93.  Rail  Bonding. 
United  Kingdom. 


No.  of 
undertakings 


Miles  of 
single  track 


Per  cent 
of  total 
(miles* 


Copper  Bonds. 

Solid  copper,  type  not  specified 

Flexible   "                                        9 

Crown— 3/0  and  4/0 20 

Neptune  4/0 19 

Chicago 8 

Forest  City 5 

Misc.  and  type  not  specified 15 

TOTAL,  copper  bonds  only 122 

Welded  Rails,  Etc. 

Continuous  rails,  type  not  specified 

Yalk  cast  weld 

Thermit 

"      and  Yalk 

"      and  Tudor 

"      and  Oxy-Acetylene 

TOTAL,  entirely  welded 8 

Partially  Welded: 

Copper  and  Thermit 31 

"         "     other  welded  joints 5 

TOTAL,  partially  welded 36 

Plastic  Bonds,  Etc. 

Plastic  bonds  and  copper 3 

"  "         "  Thermit...  1 


560. 

170. 

321. 

229.2 
71.3 
37.2 

406.8 

1801.5 


17. 
20. 
61.6 
15.9 

28. 
18. 

160.5 


1312.4 
377.3 


1689.7 


147.5 
12.3 


159.8 


47.3% 


4.2% 


44.3% 


4.2% 


122 


EUROPEAN   PRACTICE 


TABLE  7. 

94.  Use  of  Negative  Boosters. 
United  Kingdom. 


Numoer 

Miles  of 
single  track 

183 

3835. 

39 

1152. 

21  3% 

30.% 

Relation  between  Booster  Capacity  and  Plant  Capacity 

Average,  for  25  cases:  Booster  Capacity — 3.9%  of  plant  capacity. 
Highest—  9     %  for  plant  of  500  kw.  capacity 

12     %    "         "     "  800     " 
Lowest— 0.8  %    "         "     "  5725  " 

0  9   %    "  "  "  3500  "  " 


TABLE  8. 

95.  Distribution    Systems    for    Tramway    Feeders. 
United  Kingdom. 


No.  of 
undertakings 

Miles  of 
single  track 

80 

1888.2 

Conduit  "         **       i4 

63 

1839.2 

21 

626.1 

6 

40.9 

170 
11 

4394  9 

181 

EUROPEAN   PRACTICE 


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124 


EUROPEAN   PRACTICE 


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EUROPEAN   PRACTICE 


125 


TRACK  CONSTRUCTION  AND  RAILS  -  GERMANY 


Jt-Jt_-: 


™^w^^ 

Typical  Construction  for  paved  street 


STRASSBUR6 

Haarman  3  piece  Rail,  and   foot  plate 


Figure  1 1 


126 


EUROPEAN   PRACTICE 


GERMAN  TRAMWAY    RAILS 


U^Fbr  curved 
track 


RlLLENSCHIENE 

Phonix  Profit   land  la 
42.8  and  45.7.  Kg/m 


(777777//V/777777K 

VlGNOLSCHIENE 

Special  profile  for  Tramway 


(a)  Rillenschiene  with  foot  fish-plate 

OVERLAPPING  RAIL  JOINTS 


(b)  Haarman   2-piece    Rail 


& 

tys 

ji                 jl 

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(c)  and  (d)  Haarman  2-piece  Rail 


Figure  12 


EUROPEAN   PRACTICE 


127 


BRITISH  TRAMWAY  RAILS 


i  7 


Standard  prior  to    1908 


\  Present  Standard  "Brit.  Stand."  N?  4 
Bessemer  Steel  100-105  Ibs  per  yd. 
Fish  plates  2' long  63.5  Ibs.per  pair. 


Outer  fish 

plate  2'  lonq 

30.5  Ibs. 


7" 


Straight  track,  110  Ibs.  per  yard          r 


"British  Standard"  Section  R« 5.  Curved  track   116  Ibs.  per  yard. 

British  Standard   Section  N?5c. 


Figure  13 


128 


EUROPEAN   PRACTICE 


RAIL  WEIGHT  DATA 


3000?— 


Rillenscniene 
Vignolschiene 
Wechselsteg 


5902  Km 
1020  Km. 
714  Km. 


60 


1000 


750 


. 

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Figure  14 


EUROPEAN   PRACTICE 


129 


TYPICAL  RAIL  BONDS  -  UNITED   KINGDOM 


MANCHESTER 
(Standard) 


/N?  0000  Copper  Rod 


O* 


=3 


-Flexible  ;Copper  Bond. 


8- J 


GLASG  o  w 

(Standard) 


Figure  15 


130 


EUROPEAN   PRACTICE 


CROSS- BONDING  DETAFLS,  ETC  -UNITED  KINGDOM 

GLASGOW 

Standard  Cross-Bonding 


Single  Cross  Bondr*. 


Double  Rail  Bond 


40  yards  (2  rail  lengths). 


Method  of  connecting 
one  return  cable  to 
track 

LONDON 

L.C.C.  Return  Feeder  Connections 


V 

f                                                 4-N?0000  B&S  Bonds 
per  terminal,  about 
Rail                                       34"longA 

1 

±^                             Bond  Terminal  - 
5^                               clamped  and  _> 
[\        Rail                  soldered.  ^[ 

H 

f%f 

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Bare  Cable-^ 
Rail 

~i 

¥~             7 

N         Rail                                  A 

M 
Kl 

^ 

Lead  Sleeve 


Method  of  connecting 
two  return  cables  to 
track  at  same  point. 


LC.CaWe 


Figure  16 


EUROPEAN   PRACTICE  131 

96.  Electrolysis  Testing  Methods.  The  surveys  made  by 
the  engineers  of  the  Earth  Current  Commission  of  Germany  are 
systematically  planned.  They  start  with  a  general  investiga- 
tion of  geological  conditions,  the  character  of  the  soil,  ground 
water,  and  so  forth,  continuing  with  a  general  survey  of  the 
present  condition  of  the  railway  property,  including  distribu- 
tion of  load,  track  and  rail  resistance,  location  and  loading  of 
supply  and  return  circuit  cables,  and  any  other  electrical  data 
relating  to  the  investigation.  The  surveys  then  take  up  the 
specific  measurements  relating  to  stray  current,  such  as  poten- 
tial differences  between  pipes  and  rails,  current  in  pipes,  and 
so  forth.  The  surveys  conclude  generally  with  recommenda- 
tions for  betterments  where  such  are  needed,  and  often  include 
estimates  of  the  cost  of  such  improvements. 

In  England  very  little  testing  is  done  to  investigate  electrolysis 
questions  and  no  technique  has  been  developed  for  such  work. 
The  only  extensive  work  in  recent  years  is  that  of  the  Cunliffe 
brothers,  and  their  work  was  directed  mainly  toward  the  in- 
vestigation of  certain  theoretical  questions  rather  than  toward 
the  systematic  investigation  of  any  railway  system.  The 
work  of  the  Cunliffes  appears  in  two  papers  presented  by  them 
before  the  British  Institution  of  Electrical  Engineers. 

97.  Abstract  of  Laws  and  Regulations  or  Recognized  Standards 
in  European  Countries. 

(See  next  page.) 


132 


EUROPEAN    PRACTICE 


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Up, 


EUROPEAN  PRACTICE  133 

L.    MISCELLANEOUS   NOTES. 
98.  Plan   of  German   Earth    Current   Commission   Reports. 

In  abstracting  these  reports  we  have  selected  at  random 
characteristic  studies  which  would  illustrate  the  method  pur- 
sued in  the  investigations.  We  have  not  made  any  attempt 
at  all  to  select  studies  for  direct  comparison  with  any  specific 
American  condition.  In  interpreting  these  results,  the  above 
qualifications  should,  therefore,  be  kept  in  mind. 

The  reports  are  quite  uniform  in  character  and  contain  in 
general  the  following  data : 

I.  Maps  showing  the  location  and  extent  of  the  tram- 
way,   water   pipe   and   gas   pipe   systems,   location   of  the 
generating  station  or  stations,  points  of  connection  of  the 
supply  and  return  feeders. 

II.  Soil — kind  (clay,  sand,  loam,  etc.)  moisture  content, 
chemical  composition,  resistance  per  cubic  meter. 

III.  Pavements — (in  some  cases  only). 

IV.  Piping  systems — both  water  and  gas  pipes.     Total 
length,  diameter,  material,  age,  depth  below  surface,  kind 
of  joints,   resistance   of  pipe   only  and   of  pipe  including 
joints. 

V.  Tramway  system. 

(a)  General    details    of    ownership    and    operation,    car 
schedule,  maximum  and  average  loads. 

(b)  Track  and  rails — total  miles  of  single  and  double 
tracks,    gauge,    rail    profile    and    cross    section,    standard 
length,   resistance  of  rail  alone  and  including  bonds. 

(c)  Rail  bonds  and  cross  bonds,  type,  cross  section,  per 
cent  increase  in  rail  resistance  caused  by  bonds. 

(d)  Feeders,    both    supply    and    return    feeders — length 
each,  cross  section,  total  weight  of  copper,  current — maxi- 
mum and  average,  return  feeders  bare  or  insulated  and 
with  or  without  regulating  resistance. 

VI.  Tests. 

(a)  Voltage  between  pipes   and  rails,   maximum,   mini- 
mum and  average,  with  polarity,  determined  at  numerous 
points  on  the  system. 

(b)  Voltage  drop  per  kilometer  on  pipes  and  on  rails, 
and  calculated  current  flowing  on  pipes. 

(c)  Determination  by  means  of  telephone  wires  of  the 
relative  potential  of  various  points  on  the  piping  and  on 
the  rail  systems. 

VII.  Excavations  in  likely  places  to  determine  the  ex- 
istence and  extent  of  the  electrolytic  damage. 

VIII.  Plates  accompany  the  reports,  giving  graphically 
many  of  the  above  data,  frequently  on  transparent   paper 
so  that  when  placed  over  the  city  map  the  details  of  streets, 
railroads,  etc.  can  be  observed. 


134  EUROPEAN  PRACTICE 

Reasoning  from  the  data  contained  in  the  body  of  the  report, 
recommendations  are  made  for  improving  conditions,  some- 
times accompanied  by  an  estimate  of  cost.  In  some  cases  a 
supplementary  report  is  made  which  shows  the  conditions  after 
the  changes  recommended  had  been  made,  in  whole  or  in  part' 

99.  General  Comments  on  Reports.  The  electrolysis  troubles 
in  all  cases  were  confined  to  a  few  localities,  and  in  no  case  was  the 
yearly  cost  of  repairs  of  such  amount  that,  on  the  surf  ace,  would 
justify  large  expenditure  of  money  for  improvements.  The  Com- 
mission, however,  while  recognizing  the  importance  of  the 
financial  aspect  of  the  problem,  still  recommended  the  adoption 
of  the  relatively  expensive  remedies  for  the  reason  they  state 
"that  the  repairs  will  certainly  become  more  frequent  with 
lapse  of  time,  and  besides  the  increased  expense  so  caused, 
there  is  the  liability  of  service  interruption,  disturbance  of 
traffic,  pavement  replacement  and  even  danger  of  explosion 
to  be  considered." 


BIBLIOGRAPHY  135 


V.  BIBLIOGRAPHY 

This  committee  has  made  a  complete  search  of  the  Ameri- 
can literature  on  the  subject  of  electrolysis,  but  in  compiling 
the  following  bibliography  no  attempt  has  been  made  to  list 
this  literature  in  its  entirety.  This  bibliography  may  be 
considered  a  selected  list  of  such  contributions  to  the  subject 
known  to  the  committee,  as,  in  its  opinion,  are  of  permanent 
value. 

Bureau  of  Standards  Publications:    The  following  Techno- 
logic   Papers   upon   electrolysis   have   been   published   by   the 
Bureau  of  Standards  at  Washington,  D.  C. 
No.  15.  Surface  Insulation  of  Pipes  as  a  Means  of  Preventing 

Electrolysis. 

No.  18.  Electrolysis  in  Concrete. 
No.  25.  Electrolytic  Corrosion  of  Iron  in  Soils. 
No.  26.  Earth  Resistance  and  its  Relation  to  Electrolysis  of 

Underground  Structures. 

No.  27.   Special  Studies  in  Electrolysis  Mitigation. 
No.  28.  Methods  of  Making  Electrolysis   Surveys. 
No.  32.  Special    Studies    in    Electrolysis    Mitigation,    No.    2, 

Electrolysis  from  Electric  Railway  Currents  and  its 

Prevention — Experimental    Test    on    a    System    of 

Insulated  Negative  Feeders  in  St.  Louis. 
No.  52.  Electrolysis  and  Its  Mitigation. 
No.  54.   Special    Studies    in    Electrolysis    Mitigation,    No.    3. 

A  Report  on  Conditions  in  Springfield,  Ohio,  with 

Insulated  Feeder  System  Installed. 
No.  55.  Special   Studies  in  Electrolysis   Mitigation  in  Elyria, 

Ohio,  with  Recommendations  for  Mitigation. 
No.  62.  Modern  Practice  in  the  Construction  and  Maintenance 

of  Rail  Joints  and  Bonds  in  Electric  Railways. 
No.  63.  Leakage  of  Current  from  Electric  Railways. 
No.  72.  Influence  of  Frequency  of  Alternating  or  Infrequently 

Reversed  Current  on  Electrolytic  Corrosion. 
No.  75.  Data  on  Track  Leakage. 


136  BIBLIOGRAPHY 

Deiser,  George  F.  "The  Law  Relating  to  Conflicting  Uses 
of  Electricity  and  Electrolysis,"  T.  &  J.  W.  Johnson  Co., 
Philadelphia,  Pa.,  1911. 

Farnham,  Isiah  H.  "Destructive  Effect  of  Electric  Currents 
on  Subterranean  Metal  Pipes,"  Trans.  A.  I.  E.  E.,  1894. 

This  paper  probably  covers  the  first  investigation  under- 
taken of  real  scientific  value.  The  discussion  of  the  paper  is 
also  important  and  interesting. 

"Means  for  Preventing  Electrolysis  of  Buried  Metal  Pipes," 
Gassier s  Magazine,  August,  1895. 

This  article  is  of  particular  interest,  in  that  it  shows  that 
at  a  very  early  date  the  value  of  the  insulated  negative  feeder 
system  as  a  means  of  mitigating  electrolysis  was  recognized. 

Ganz,  Albert  F.  "Electrolytic  Corrosion  of  Iron  by  Direct 
Current  in  Street  Soils,"  Trans.  A.  I.  E.  E.,  Vol.  XXXI,  p. 
1167,  1912. 

This  paper  gives  the  results  of  a  laboratory  investigation  of 
considerable  scientific  value  and  interest. 

"Electrolysis  from  Stray  Electric  Currents,"  Proc.  New 
England  Association  of  Gas  Engineers,  1913. 

This  paper  treats  the  subject  in  a  popular,  but  nevertheless 
scientifically  correct  manner,  and  leads  to  the  conclusion  that 
the  insulated  negative  feeder  system  is  the  logical  one  to  employ 
for  the  purpose  of  mitigating  electrolysis. 

"Effects  of  Electrolysis  on  Engineering  Structures,"  Trans. 
Inter.  Eng.  Congress,  San  Francisco,  Cal.,  1915. 

This  paper  gives  a  review  of  electrolysis  conditions  and  of 
mitigating  methods  in  America  with  a  brief  statement  of  the 
electrolysis  situation  in  Europe. 

Haber,  F.,  and  Goldschmidt,  F.  "Der  Anodische  Angriff 
des  Eisens  Durch  Vagabundierende  Strome  im  Erdreich  und 
die  Passivitat  des  Eisens."  (The  Corrosion  of  Iron  by  Stray 
Currents  in  the  Ground  and  the  Passivity  of  Iron.)  Zeitschrift 
fur  Electrochemie,  January  26,  1906.  Breslau. 

A  paper  of  considerable  scientific  value,  particularly  with 
respect -to  the  electrochemistry  of  the  subject.  In  so  far  as 
is  known  no  English  translation  exists. 

Harper,  Robert  B.  "Comparative  Values  of  Various  Coat- 
ings and  Coverings  for  the  Prevention  of  Soil  and  Electrolytic 


BIBLIOGRAPHY  137 

Corrosion  of  Iron  Pipe,"  Proc.  Illinois  Gas  Association,  Vol. 
5,  1909. 

A  paper  based  upon  a  rather  elaborate  series  of  tests  carried 
out  in  a  thoroughly  scientific  manner  on  many  coatings  and 
coverings,  leading  to  the  conclusion  that  no  coatings  or  cover- 
ings are  of  permanent  value  in  positive  areas.  Of  all  coatings 
investigated,  dips  of  coal  tar  pitch  applied  hot,  were  found  to 
be  best.  Paints  were  found  to  be  practically  useless. 

Hayden,  J.  L.  R.  "Alternating-Current  Electrolysis,"  Trans, 
A.  I.  E.  E.,  1907.  Vol.  26,  Part  I. 

A  report  of  a  laboratory  investigation  tending  to  show  that 
alternating  current  electrolysis  is  small  as  compared  with  direct 
current  electrolysis.  The  tests  also  bring  out  the  inhibiting 
effect  of  the  superposition  of  a  small  direct  current. 

Jackson,  Dugald  C.  "Corrosion  of  Iron  Pipes  by  Action  of 
Electric  Railway  Currents."  Journal  of  Association  of  En- 
gineering Societies,  September,  1894. 

An  account  of  some  early  laboratory  investigations  carried 
out  at  the  University  of  Wisconsin,  in  which  it  was  definitely 
proven  that  corrosion  due  to  electrolysis  could  take  place  at 
very  low  voltages — considerably  lower  voltages  than  are  re- 
quired to  decompose  water. 

Michalke,  Carl.  "Stray  Currents  from  Electric  Rail  ways." 
Translated  and  edited  by  Otis  Allen  Kenyon,  McGraw  Publish- 
ing Company,  New  York  City,  1906. 

A  relatively  non-mathematical,  though  scientific  and  valu- 
able treatment  of  the  subject. 

Rhodes,  George  I.  "Some  Theoretical  Notes  on  the  Re- 
duction of  Earth  Currents  from  Electric  Railway  Systems,  by 
Means  of  Negative  Feeders."  Trans.  A.  I.  E.  E.,  Vol.  XXVI, 
p.  247,  1907. 

A  mathematical  paper  showing  quantitatively  the  difference 
in  effectiveness  of  copper  paralleling  the  rails  and  insulated 
negative  feeders  in  reducing  stray  currents. 

Schaffer,  Guy  F.  "Corrosion  of  Iron  Embedded  in  Con- 
crete." Engineering  Record,  July  30,  1910. 

This  is  a  report  of  a  series  of  tests  made  at  the  Massachusetts 


138  BIBLIOGRAPHY 

Institute  of  Technology,  carried  out  with  the  view  of  obtain- 
ing some  data  on  the  effect  of  currents  of  low  potential  on  steel 
embedded  in  concrete.  The  study  included  the  effect  on  steel 
in  both  the  stressed  and  unstressed  condition,  also  the  effect 
of  setting  cement  on  paint  films.  It  was  shown  (a),  that  con- 
crete does  not  act  as  an  insulator;  (b),  that  iron  under  stress 
does  not  go  into  solution  as  rapidly  as  unstressed  iron;  and 
(c),  that  the  paints  used  to-day  for  structural  work  embedded 
in  concrete  do  not  fulfill  the  conditions  of  proper  protection 
from  electrolytic  action,  and  it  is  doubtful  whether  they  are 
of  use  for  protection  in  any  sense  after  a  lapse  of  some  months. 

Sever,  George  F.  "Electrolysis  of  Underground  Conductors." 
Trans.  International  Electrical  Congress,  St.  Louis,  Vol.  3, 
p.  666,  1904. 

This  is  a  summary  in  tabular  form,  consisting  of  street  rail- 
way practice,  municipal  reports,  ordinances  and  letters  in  force 
in  the  United  States  at  the  time  the  report  was  prepared,  1904. 
The  discussion  which  followed  the  presentation  of  this  report 
is  of  interest. 

Stone,  Charles  A.  and  Howard  C.  Forbes.  "Electrolysis  of 
Water  Pipes."  New  England  Water  Works  Association,  Vol. 
9,  1894-95. 

This  is  the  report  of  the  results  of  an  investigation  of  elec- 
trolysis conditions  in  Boston.  It  is  one  of  the  best  early  papers 
on  the  subject.  The  discussion  of  this  paper  is  interesting. 

Topical  Discussion  on  Electrolysis.  Proc.  New  England 
Water  Works  Association,  Vol.  XX,  1905. 

This  is  the  report  of  a  discussion  entered  into  by  various 
New  England  Water  Works  superintendents.  Several  phases 
of  the  discussion  are  instructive. 


APPENDICES 


139 


VI.  APPENDICES. 
100.  Resistance  of  Standard  Cast  Iron  Pipe. 

Note:  The  values  given  in  this  table  are  for  one  assumed  specific  re- 
sistance for  cast  iron,  wrought  iron  and  steel,  respectively.  For  exceed- 
ingly accurate  work,  measures  should  be  taken  to  determine  the  actual 
specific  resistance  of  the  metal  under  test.  Experience  has  shown  that 
this  may  vary  widely  from  that  assumed  in  the  tables;  in  other  words, 
the  table  values  can  only  be  used  for  approximate  results  unless  definite 
information  is  at  hand  as  to  the  specific  resistance  of  the  metal  under  test. 

From  pages  379  and  386,  1913,  Proceedings  American  Electric 
Railway  Engineering  Association. 

TABLE    FOR    DETERMINATION    OF    CURRENT    FLOW    ON 
PIPING  FROM   MILLI-VOLT  DROP  ALONG  CONTINUOUS 
LENGTH    OF    PIPE    BETWEEN    JOINTS. 

L  =  Distance  between  contacts  in  feet 
E  =  Instrument  reading  in  milli- volts, 
K  =  Constant  from  table. 


KE 
L 


=  Current  flow  in  amperes. 

TABLE  9 

STANDARD   CAST   IRON   PIPE. 
(Based  on  a  resistance  of  0.00144  ohm  per  Ib.  ft.) 


CLASSIFICATION 

ACTUAL  DIMENSIONS 

K  =  current 

*Asso- 

Weight 

for  one  milli- 

Nomi- 

cia- 

Class 

per  ft. 

volt  drop 

nal. 

tion 

Let- 

Head 

Press. 

Outs. 

Ins. 

exclu- 

per ft.  of 

Dia.in. 

Stand- 

terf 

Feet 

Ibs.  per 

dia. 

dia. 

sive  of 

continuous 

ard 

sq.  in. 

in. 

in. 

hub-lb. 

pipe. 

Amperes. 

4 

N 

A 

4.80 

4.12 

14.9 

10.3 

4 

N 

C 

4.80 

4.08 

15.7 

10.9 

4 

N 

E 

4.80 

4.02 

16.9 

11.7 

G 

4.80 

4.00 

17.2 

12.0 

W 

A 

100 

43 

4.80 

3.96 

18.0 

12.5 

N 

G 

5.00 

4.16 

18.9 

13.1 

N 

I 

5.00 

4.10 

20.0 

13.9 

W 

B 

200 

86 

5.00 

4.10 

20.0 

13.9 

4 

N 

K 

5.00 

4.04 

21.3 

14.8 

*W   =  American  Water  Works  Association  Standard. 
N    =  New  England  Water  Works  Association  Standard. 
G   =  American  Gas  Institute  Standard. 

t  =  As  used  by  the  American  Water  Works  Association  and  the  New  England  Water 
Works  Association. 


140 


APPENDICES 


TABLE    FOR    DETERMINATION    OF  CURRENT  FLOW  ON  STANDARD  CAST 

IRON  PIPE  FROM  MILLI-VOLT    DROP    ALONG    CONTINUOUS    LENGTH    OF 

PIPE    BETWEEN    JOINTS.      (Continued.) 


CLASSIFICATION 

ACTUAL  DIMENSIONS 

K  =  current 

*Asso- 

Weight 

for  one  milli- 

Nomi- 

cia- 

per  ft. 

volt  drop 

nal. 

tion 

Class 

Head 

Press. 

Outs. 

Ins. 

exclu- 

per ft.   of 

Dia.in. 

Stand- 

Letter 

Feet 

Ibs.  per 

dia. 

dia. 

sive  of 

continuous 

ard 

t 

sq.  in. 

in. 

in. 

hub-lb. 

pipe. 

Amperes. 

4 

W 

C 

300 

130 

5.00 

4.04 

21.3 

14.8 

4 

w 

D 

400 

173 

5.00 

3.96 

22.8 

15.8 

6 

N 

A 

6.90 

6.14 

24,3 

16.9 

6 

N 

C 

.  .  . 

6.90 

6.06 

26.7 

18.5 

6 

G 

... 

6.90 

6.04 

27.2 

18.9 

6 

W 

A 

100 

43 

6.90 

6.02 

27.8 

19.3 

6 

N 

E 

6.90 

5.98 

29.1 

20.2 

6 

W 

B 

200 

86 

7.10 

6.14 

31.1 

21.6 

6 

N 

G 

7.10 

6.10 

32.4 

22.5 

6 

W 

C 

300 

130 

7.10 

6.08 

32.9 

22.8 

6 

N 

I 

7.10 

6.02 

34.8 

24.2 

6 

W 

D 

400 

173 

7.10 

6.00 

35.3 

24.5 

6 

W 

E 

500 

217 

7.22 

6.06 

37.7 

26  2 

6 

w 

F 

600 

260 

7.22 

6.00 

39.6 

27.4 

6 

w 

G 

700 

304 

7.38 

6.08 

42.8 

29.7 

6 

w 

H 

800 

347 

7.38 

6  00 

45.2 

31.4 

8 

N 

A 

9.05 

8.21 

35  5 

24.7 

8 

G 

9.05 

8.15 

37.9 

26.3 

8 

W 

A 

100 

43 

9.05 

8.13 

38.7 

26.9 

8 

N 

C 

9.05 

8.09 

40.3 

28.0 

8 

W 

B 

200 

86 

9.05 

8.03 

42.7 

29.6 

8 

N 

E 

... 

9.05 

7.99 

44.3 

30.7 

8 

W 

C 

300 

130 

9.30 

8.18 

47.9 

33.3 

8 

N 

G 

9.30 

8.14 

49.6 

34.5 

8 

W 

D 

400 

173 

9.30 

8.10 

51.2 

35.5 

8 

N 

I 

9.30 

8.04 

53.6 

37  2 

8 

W 

E 

500 

217 

9.42 

8.10 

56.7 

39.4 

8 

W 

F 

600 

260 

9.42 

8.00 

60.6 

42.1 

8 

w 

G 

700 

304 

9.60 

8.10 

65.0 

45.1 

8 

w 

H 

800 

347 

9.60 

8.00 

69.0 

48.0 

10 

N 

A 

11.10 

10.16 

49.0 

34  0 

10 

G 

11.10 

10.12 

51.0 

35.4 

10 

N 

B 

11.10 

10.10 

51.9 

36.1 

APPENDICES 


141 


TABLE    FOR    DETERMINATION    OF  CURRENT  FLOW  ON  STANDARD  CAST 

IRON  PIPE  FROM  MILLI-VOLT    DROP    ALONG    CONTINUOUS    LENGTH    OF 

PIPE    BETWEEN    JOINTS.     (Continued.) 


CLASSIFICATION 

ACTUAL  DIMENSIONS 

K-current 

"•Asso- 

Weight 

for  one  milli- 

Nomi- 

cia- 

per ft. 

volt  diop 

nal. 

tion 

Class 

Head 

Press. 

Outs. 

Ins. 

exclu- 

pei   ft.  of 

Dia.in. 

Stand- 

Letter 

Feet 

Ibs.  per 

dia. 

aia. 

sive  of 

continuous 

ard 

t 

sq.  in. 

in. 

in. 

hub-lb. 

pipe. 

Amperes. 

10 
10 

W 

N 

A 

C 

100 

43 

11.10 
11.10 

10.10 
10.04 

51.9 
54.9 

36.1 
38.1 

10 

N 

D 

11.10 

9.98 

57.9 

40.2 

10 

W 

B 

200 

86 

11.10 

9.96 

58.9 

40.9 

10 

N 

E 

11.40 

10.20 

63.6 

44.1 

10 

W 

C 

300 

130 

11.40 

10.16 

65.5 

45.5 

10 

N 

F 

11.40 

10.14 

66.5 

46.2 

10 

N 

G 

11.40 

10.06 

70.5 

49.0 

10 

W 

D 

400 

173 

11.40 

10.04 

71.5 

49.7 

10 

N 

H 

11.40 

10.00 

73  5 

51.1 

10 

W 

E 

500 

217 

11.60 

10.12 

78.7 

54.6 

10 

W 

F 

600 

260 

11.60 

10.00 

84.6 

58.8 

10 

W 

G 

700 

304 

11.84 

10.12 

92.4 

64.1 

10 

W 

H 

800 

347 

11.84 

10.00 

98.5 

68.4 

12 

N 

A 

13.20 

12.22 

61.1 

42.5 

12 

N 

B 

13.20 

12.14 

65.9 

45.7 

12 

G 

•• 

... 

13.20 

12.12 

67.0 

46.5 

12 

W 

A 

100 

43 

13.20 

12.12 

67.0 

46.5 

12 

N 

C 

13.20 

12.06 

70.6 

49.0 

12 

N 

D 

13.20 

11.98 

75.3 

52.3 

12 

W 

B 

200 

86 

13.20 

11.96 

76.4 

53.0 

12 

N 

E 

13.50 

12.20 

81.9 

56.8 

12 

W 

C 

300 

130 

13.50 

12.14 

85.5 

59.4 

12 

N 

F 

13.50 

12.12 

86.6 

60.2 

12 

N 

G 

.  .  . 

13.50 

12.04 

91.5 

63.6 

12 

W 

D 

400 

173 

13.50 

12.00 

93.8 

65.1 

12 

N 

H 

13.50 

11.96 

96.2 

66.8 

12 

W 

E 

500 

217 

13.78 

12.14 

104.0 

72.3 

12 

W 

F 

600 

260 

13.78 

12.00 

112.0 

77.9 

12 

W 

G 

700 

304 

14.08 

12.14 

125.0 

86.7 

12 

W 

H 

800 

347 

14.08 

12.00 

133.0 

92.4 

14 

N 

A 

15.30 

14.24 

76.8 

53.4 

14 

N 

B 

15.30 

14   16 

82.3 

57.1 

14 

W 

A 

100 

43 

15.30 

14.16 

82.3 

57.1 

142 


APPENDICES 


TABLE   FOR    DETERMINATION    OP    CURRENT   FLOW  ON  STANDARD  CAST 
IRON  PIPE  FROM  MILLI-VOLT   DROP  ALONG  CONTINUOUS  LENGTH 
OF  PIPE  BETWEEN  JOINTS.      (Continued.) 


CLASSIFICATION 

ACTUAL  DIMENSIONS 

K  —  current 

*Asso- 

Weight 

for  one  milli- 

Nomi- 

cia- 

per  ft. 

volt  drop 

nal. 

tion 

Class 

Head 

Press. 

Outs. 

Ins. 

exclu- 

per ft.   of 

Dia.in. 

Stand- 

Letter 

Feet 

Ibs.  per 

dia. 

dia. 

sive  of 

continuous 

ard 

t 

sq.  in. 

in. 

in. 

hub-lb. 

pipe. 

Amperes. 

14 

N 

C 

15.30 

14.08 

87.9 

61.0 

14 

N 

D 

15.30 

13.98 

94.8 

65.8 

14 

W 

B 

200 

86 

15.30 

13.98 

94.8 

65.8 

14 

N 

E 

15.65 

14.25 

103.0 

71.4 

14 

W 

C 

300 

130 

15.65 

14.17 

108.0 

75.0 

14 

N 

F 

... 

15.65 

14.15 

109.0 

76.2 

14 

N 

G 

15.65 

14.07 

115.0 

80.0 

14 

W 

D 

400 

173 

15.65 

14.01 

119.0 

82.8 

14 

N 

H 

15.65 

13.99 

121.0 

83.9 

14 

W 

E 

500 

217 

15.98 

14.18 

133.0 

92.4 

14 

W 

F 

600 

260 

15.98 

14.00 

145.0 

'      101.0 

14 

W 

G 

700 

304 

16.32 

14.18 

160.0 

111.0 

14 

W 

H 

800 

347 

16.32 

14.00 

172.0 

120.0 

16 

N 

A 

17.40 

16.30 

90.9 

63.1 

16 

N 

B 

. 

17.40 

16.20 

98.9 

68.6 

16 

W 

A 

100 

43 

17.40 

16.20 

98.9 

68.6 

16 

G 

17.40 

16.16 

102.0 

70.7 

16 

N 

C 

; 

17.40 

16.10 

107.0 

74.1 

16 

N 

D 

17.40 

16.00 

115.0 

79.6 

16 

W 

B 

200 

86 

17.40 

16.00 

115.0 

79.6 

16 

N 

E 

17.80 

16  30 

125.0 

87.1 

16 

N 

F 

17.80 

16.20 

133.0 

92.6 

16 

W 

C 

300 

130 

17.80 

16.20 

133.0  " 

92.6 

16 

N 

G 

17.80 

16.10 

141.0 

98.2 

16 

W 

D 

400 

173 

17.80 

16.02 

147.0 

102.3 

16 

N 

H 

17.80 

16.00 

149.0 

103.5 

16 

W 

E 

500 

217 

18.16 

16.20 

165.0 

114.5 

16 

W 

F 

600 

260 

18.16 

16.00 

181.0 

125.5 

16 

W 

G 

700 

304 

18.54 

16.18 

201.0 

139.5 

16 

W 

H 

800 

347 

18.54 

16.00 

215.0 

149.0 

18 

N 

A 

19.25 

18.11 

104.0 

72.5 

18 

N 

B 

19.25 

17.99 

115.0 

79.8 

18 

W 

A 

100 

43 

19.50 

18.22 

118.0 

82.2 

18 

N 

C 

19.50 

18.12 

127.0 

88.5 

18 

N 

D 

19.50 

18.00 

138.0 

95.8 

18 

W 

B 

200 

86 

19.50 

18.00 

138.0 

95  8 

APPENDICES 


143 


TABLE  FOR  DETERMINATION   OF    CURRENT    FLOW  ON    STANDARD    CAST 
IRON    PIPE    FROM  MILLI-VOLT  DROP    ALONG    CONTINUOUS    LENGTH 
OF  PIPE  BETWEEN  JOINTS.      (Continued.} 


CLASSIFICATION 

ACTUAL  DIMENSIONS 

K.  —  current 
'or  one  milli- 

*Asso- 

Weight 

volt  drop 

Nomi- 

cia- 

Ins. 

per  ft. 

per  ft.   of 

nal. 

tion 

Class 

Head 

Press. 

Outs. 

dia. 

exclu- 

continuous 

Dia.  in. 

Stand- 

Letter 

Feet 

Ibs.  per 

dia. 

in. 

sive  of 

pipe. 

ard 

t 

sq.  in. 

in. 

hub-lb. 

Amperes. 

18 

N 

E 

19.70 

18.10 

148.0 

103.0 

18 

N 

F 

19.70 

17.98 

159.0 

110.4 

18 

W 

C 

300 

130 

19.92 

18.18 

162.0 

113.0 

18 

W 

D 

400 

173 

19.92 

18.00 

178.0 

123.8 

18 

W 

E 

500 

217 

20.34 

18.20  . 

202.0 

140.5 

18 

W 

F 

600 

260 

20  34 

18.00 

220.0 

152.6 

18 

W 

G 

700 

304 

20.78 

18.22 

245.0 

170.0 

18 

W 

H 

800 

347 

20.78 

18.00 

264.0 

183.3 

20 

N 

A 

21.30 

20.10 

122.0 

84.6 

20 

N 

B 

21.30 

19.98 

134.0 

93.0 

20 

W 

A 

100 

43 

21.60 

20.26 

137.0 

95.4 

20 

G 

21.60 

20.24 

140.0 

97.0 

20 

N 

C 

21.60 

20.16 

147.0 

102.5 

20 

N 

D 

21.60 

20.02 

161.0 

112.0 

20 

W 

B 

200 

86 

21.60 

20.00 

163.0 

113.0 

20 

N 

E 

21.90 

20.20 

175.0 

122.0 

20 

N 

F 

21.90 

20.06 

189.0 

131.0 

20 

W 

C 

300 

130 

22.06 

20.22 

191.0 

132.0 

20 

W 

D 

400 

173 

22.06 

20.00 

212.0 

148.0 

20 

W 

E 

500 

217 

22.54 

20.24 

241.0 

167.0 

20 

W 

F 

600 

260 

22.54 

20.00 

265.0 

184.0 

20 

W 

G 

700 

304 

23.02 

20.24 

295.0 

205.0 

20 

W 

H 

800 

347 

23.02 

20.00 

319.0 

221.0 

24 

N 

A 

25.40 

24.12 

156.0 

108.0 

24 

N 

B 

25.40 

23.96 

174.0 

121.0 

24 

G 

25.80 

24.28 

187.0 

130.0 

24 

W 

A 

100 

43 

25.80 

24.28 

187.0 

130.0 

24 

N 

C 

25.80 

24.20 

196.0 

136.0 

24 

N 

D 

25.80 

24.04 

215.0 

149.0 

24 

W 

B 

200 

86 

25.80 

24.02 

217.0 

151.0 

24 

N 

E 

26.10 

24  .  20 

234.0 

163.0 

24 

N 

F 

26.10 

24.04 

253.0 

176.0 

24 

W 

C 

300 

130 

26.32 

24.24 

258.0 

179.0 

24 

W 

D 

400 

173 

26.32 

24.00 

286.0 

198.0 

24 

W 

E 

500 

217 

26.90 

24.28 

328.0 

228.0 

24 

W 

F 

600 

260 

26.90 

24.00 

362.0 

251.0 

144 


APPENDICES 


TABLE    FOR    DETERMINATION    OF    CURRENT  FLOW  ON  STANDARD  CAST 

IRON  PIPE  FROM  MILLI-VOLT    DROP    ALONG    CONTINUOUS    LENGTH    OF 

PIPE    BETWEEN     JOINTS.     (Continued.) 


CLASSIFICATION 

ACTUAL  DIMENSIONS 

K.  —  current 
for  one  milli- 

*Asso- 

Weight 

volt  drop 

Nomi- 

cia- 

per  ft. 

per  ft.   of 

nal. 

tion 

Class 

Head 

Press. 

Outs. 

Ins. 

exclu- 

continuous 

Dia.in. 

Stand- 

Letter 

Feet 

Ibs.  per 

dia. 

dia. 

sive  of 

pipe. 

ard 

t 

sq.  in. 

in. 

in. 

hub-lb. 

Amperes. 

30 

N 

A 

31.60 

30.18 

215.0 

149.0 

30 

N 

B 

31.60 

29.98 

245.0 

170.0 

30 

G 

31.74 

30.04 

257.0 

179.0 

30 

W 

A 

100 

43 

31.74 

29.98 

266.0 

185.0 

30 

N 

c 

32.00 

30.18 

277.0 

192.0 

30 

N 

D 

32.00 

29.98 

306.0 

213.0 

30 

W 

B 

200 

86 

32.00 

29.94 

312.0 

217.0 

30 

N 

E 

32.40 

30.20 

337.0 

234.0 

30 

N 

F 

32.40 

30.00 

367.0 

255.0 

30 

W 

C 

300 

130 

32.40 

30.00 

367.0 

255.0 

30 

W 

D 

400 

173 

32.74 

30.00 

422.0 

292.0 

30 

W 

E 

500 

217 

33.10 

30.00 

479.0 

333.0 

30 

W 

F 

600 

260 

33  .  46 

30.00 

537.0 

373.0 

36 

N 

A 

37.80 

36.22 

287.0 

199.0 

36 

N 

B 

37  .  80 

36.00 

326.0 

226.0 

36 

G 

37.96 

36.06 

345.0 

239.0 

36 

W 

A 

100 

43 

37.96 

35.98 

358.0 

248.0 

36 

N 

C 

38.30 

36.26 

373.0 

259.0 

36 

N 

D 

... 

38.30 

36.04 

412.0 

286.0 

36 

W 

B 

200 

86 

38.30 

36.00 

418.0 

290.0 

36 

N 

E 

38.70 

36.20 

459.0 

319.0 

36 

W 

C 

300 

130 

38.70 

35  98 

497.0 

346.0 

36 

N 

F 

38.70 

35.96 

502.0 

349.0 

36 

W 

D 

400 

173 

39.16 

36.00 

581.0 

404.0 

36 

W 

E 

500 

217 

39.60 

36.00 

666.0 

463.0 

36 

W 

F 

600 

260 

40  04 

36.00 

753.0 

523.0 

42 

N 

A 

44.00 

42.26 

368.0 

256.0 

42 

N 

B 

44.00 

42.00 

422.0 

293.0 

42 

G 

44.20 

42.06 

452.0 

314.0 

42 

W 

A 

100 

43 

44.20 

42.00 

465.0 

323.0 

42 

N 

C 

44.50 

42.24 

480.0 

333.0 

42 

N 

D 

44.50 

41.96 

538.0 

374.0 

42 

W 

B 

200 

86 

44.50 

41.94 

542.0 

376.0 

42 

N 

E 

.  .  . 

45.10 

42.30 

600.0 

416.0 

42 

N 

F 

45.10 

42.04 

654.0 

454.0 

APPENDICES 


145 


TABLE    FOR    DETERMINATION    OF    CURRENT  FLOW  ON  STANDARD  CAST 

IRON    PIPE  FROM  MILLI-VOLT    DROP    ALONG    CONTINUOUS    LENGTH    OF 

PIPE  BETWEEN  JOINTS.     (Continued.) 


CLASSIFICATION 

ACTUAL  DIMENSIONS 

K.  —  current 

:or  one  milli- 

Asso- 

Weight 

volt  drop 

Nomi- 

cia- 

Class 

Head 

Press. 

Outs. 

Ins. 

per  ft. 

per  ft.   of 

nal 

tion 

Letter 

Feet 

Ibs.  per 

dia. 

dia. 

exclu- 

continuous 

dia.in. 

Stand- 

t 

sq.  in. 

in. 

in. 

sive  of 

pipe. 

ard 

hub-lb. 

Amperes. 

42 

W 

C 

300 

130 

45.10 

42.02 

657.0 

456.0 

42 

W 

D 

400 

173 

45.58 

42.02 

763.0 

530.0 

48 

N 

A 

50.20 

48.30 

459  0 

319.0 

48 

N 

B 

.  .  . 

50.20 

48  .  00 

529.0 

367.0 

48 

N 

C 

... 

50.80 

48.30 

608.0 

422.0 

48 

G 

50.50 

47.98 

608.0 

422.0 

48 

W 

A 

100 

43 

50.50 

47.98 

608.0 

422  0 

48 

N 

D 

50.80 

48.00 

678.0 

471.0 

48 

W 

B 

200 

86 

50.80 

47.96 

686.0 

477.0 

48 

N 

E 

51.40 

48.30 

757.0 

526.0 

48 

N 

F 

51.40 

48.00 

828  0 

575.0 

48 

W 

C 

300 

130 

51.40 

47.98 

832.0 

578.0 

48 

W 

D 

400 

173 

51.98 

48.06 

961.0 

667.0 

54 

N 

A 

56.40 

54.34 

559.0 

388.0 

54 

N 

B 

56.40 

54.00 

650.0 

452.0 

54 

W 

A 

100 

43 

56.66 

53.96 

731.0 

508.0 

54 

N 

C 

57.10 

54.36 

750.0 

521.0 

54 

N 

D 

57.10 

54.02 

840.0 

583.0 

54 

W 

B 

200 

86 

57.10 

54.00 

845.0 

586.0 

54 

N 

E 

57.80 

54.26 

946.0 

657.0 

54 

N 

F 

57.80 

54.00 

1041.0 

723.0 

54 

W 

C 

300 

130 

57.80 

54.00 

1041.0 

723.0 

54 

W 

D 

400 

173 

58.40 

53.94 

1230.  0 

854.0 

60 

N 

A 

62.60 

60.40 

664.0 

460  0 

60 

N 

B 

62.60 

60.00 

782.0 

543.0 

60 

W 

A 

100 

43 

62.80 

60.02 

836.  '0 

581  0 

60 

N 

C 

63.40 

60.40 

910.0 

632.0 

60 

W 

B 

200 

86 

63.40 

60.06 

1010.0 

701.0 

60 

N 

D 

...       ' 

63.40 

60.00 

1028.0 

714.0 

60 

N 

E 

64.20 

60.40 

1160.0 

806.0 

60 

W 

C 

300 

130 

64.20 

60.20 

1220.0 

848.0 

60 

N 

F 

64.20 

60.00 

1280.0 

889.0 

60 

W 

D 

400 

173 

64.82 

60.06 

1455.0 

1010.0 

72 

W 

A 

100 

43 

75.34 

72.08 

1178.0 

819.0 

72 

W 

B 

200 

86 

76.00 

72.10 

1415.0 

983.0 

72 

W 

C 

300 

130 

76.88 

72.10 

1745.0 

1212.0 

84 

W 

A 

100 

43 

87.54 

84.10 

1445.0 

1005.0 

84 

W 

B 

200 

86 

88  54 

84.10 

1878.0 

1304.0 

146 


APPENDICES 


101.     Resistance  of  Standard  Steel  or  Wrought  Iron  Pipe. 

TABLE  10 

STANDARD  STEEL  (Or  Wrought  Iron)  PIPE. 
(Based  on  Resistance  of  steel  0.00021  ohms   per  Ib.   ft.      Based   on 
sistance  of  wrought  iron  0.000181  ohm  per  Ib.  ft.) 


Actual  Dimensions 

K  =  current  for  one  millivolt 

Weight 

drop  per  ft.  of  continuous 

Nomi- 

per ft. 

pipe-amperes. 

nal 

Classifi- 

Outside 

Inside 

plain  ends- 

dia.  in. 

cation 

diameter 

diameter 

steel-lb. 

inches 

inches 

Steel 

Wrought  iron 

1/8 

S 

0.405 

0.269 

0.244 

1.16 

1   32 

1/8 

X 

0.405 

0.215 

0.314 

1.50 

1.70 

1/4 

s 

0.540 

0.364 

0.424       . 

2.02 

2.30 

1/4 

X 

0.540 

0.302 

0.535 

2.55 

2.  go 

3/8 

s 

0.675 

0.493 

0.567 

2.70 

3.07 

3/8 

X 

0.675 

0.423 

0.738 

3.51 

4.00 

1/2 

s 

0.840 

0.622 

0.850 

4.05 

4.60 

1/2 

X 

0.840 

0.546 

1.09 

5,18 

5.88 

1/2 

XX 

0.840 

0.252 

1.71 

8.16 

_  9.28 

3/4 

s 

1.050 

0.824 

1.13 

5.38 

6.11 

3/4 

X 

1.050 

0.742 

1.47 

7.03 

7.98 

3/4 

XX 

1.050 

0.434 

2.44 

11.6 

13.2 

1 

s 

1.315 

1.049 

1.68 

7.99 

9.09 

X 

1.315 

0.957 

2.17 

10.3 

11.8 

XX 

1.315 

0.599 

3.66 

17.4 

J9.8 

1/4 

s 

1.660 

1.380 

2.27 

10.8 

12.3 

1/4 

X 

.660 

1.278 

3.00 

14.3 

16.2 

1/4 

XX 

.660 

0.896 

5.21 

24.8 

28.2 

1/2 

s 

.900 

1.610 

2.72 

12.9 

14.7 

1/2 

X 

.900 

1.500 

3.63 

17.3 

19.6 

1/2 

XX 

..900 

1.100 

6.41 

30.5 

34.7 

2 

s    . 

2.375 

2.067 

3.65 

17.4 

19.8 

2 

X 

2.375 

1.939 

5.02 

23.9 

27.2 

2 

XX 

2.375 

1.503 

9.03 

43.0 

48.8 

21/2 

s 

2.875 

2.469 

5.79 

27.6 

31.4 

2   1/2 

X 

2.875 

2.323 

7   66 

36.5 

41.5 

21/2 

XX 

2.875 

1.771 

13.69 

65.2 

74.2 

3 

s 

3.500 

3.068 

7.57 

36.0 

41.0 

3 

X 

3.500 

2.900 

10.2 

48.8 

55.6 

3 

XX 

3.500 

2.300 

18.6 

88.5 

101.0 

3   1/2 

s 

4.000 

3.548 

9.11 

43.4 

49.3 

3  1/2 

X 

4.000 

3.364 

12.5 

59.6 

67.8 

3  1/2 

XX 

4.000 

2.728 

22.8 

109.0 

124.0 

4 

s 

4.500 

4.026 

10.8 

51.4 

58.4 

4 

X 

4.500 

3.826 

15.0 

71.3 

81.1 

4 

XX 

4.500 

3.152 

27.5 

131.0 

149.0 

APPENDICES 

STANDARD  STEEL  (OR  WROUGHT  IRON)  PIPE.    Continued. 


147 


Actual  Dimensions 

K  =  current  for  one  millivolt 

Weight 

drop  per  ft.  of  continuous 

Nomi- 

per ft. 

pipe-amperes. 

nal 

Classifi- 

Outside 

Inside 

plain  ends- 

A  * 

.  • 

j  •         . 

j  •         . 

steel-lb. 

u.13,,  in. 

CciT-ion. 

inches 

inches 

Steel 

Wrought  iron 

4   1/2 

S 

5.000 

4.506 

12.5 

59.8 

67.9 

4   1/2 

X 

5.000 

4.290 

17.6 

83.9 

95  3 

4   1/2 

XX 

5.000 

3.580 

32.5 

155.0 

176.0 

5 

S 

5.563 

5.047 

14.6 

69.7 

79.2 

5 

X 

5.563 

4.813 

20.8 

98.9 

112.0 

5 

XX 

5.563 

4.063 

38.5 

183.0 

209.0 

6 

S 

6.625 

6.065 

19.0 

90.3 

103.0 

6 

X 

6.625 

5.761 

28.6 

136.0 

155.0 

6 

XX 

6.625 

4.897 

53.2 

253  .  0 

288  0 

7 

S 

7.625 

7  023 

23.5 

112.0 

127.0 

7 

X 

7.625 

6.625 

38.0 

181.0 

206.0 

7 

XX 

7  .  625 

5.875 

63.1 

300.0 

342.0 

8 

S 

8.625 

8.071 

24.7 

118.0 

134  0 

8 

S 

8.625 

7.981 

28.5 

136.0 

155*0 

8 

X 

8.625 

7.625 

43  4 

206.0 

235.0 

8 

XX 

8.625 

6  .  875 

72.4 

345  0 

392.0 

9 

S 

9.625 

8.941 

33.9 

161.0 

184.0 

9 

X 

9.625 

8.625 

48.7 

232.0 

264.0 

10 

S 

10.750 

10.192 

31.2 

149.0 

169.0 

10 

S 

10.750 

10.136 

34.2 

163.0 

185.0 

10 

S 

10.750 

10.020 

40.5 

192.0 

219.0 

10 

X 

10.750 

9.750 

54.7 

261.0 

297.0 

11 

S 

11.750 

11.000 

45.6 

217.0 

247.0 

11 

X 

11.750 

10.750 

60.1 

286.0 

326.0 

12 

S 

12.750 

12.090 

43  8 

208  .  0 

237.0 

12 

S 

12.750 

12.000 

49.6 

236.0 

269.0 

12 

X 

12.750 

1  1  .  750 

65  4 

311.0 

351.0 

13 

S 

14  .  000 

13.250 

54.6 

260.0 

296  .  0 

13- 

X 

14  000 

13.000 

72   1 

343  0 

391.0 

14 

S 

15.000 

14.250 

58  6 

279.0 

317.0 

14 

X 

15.000 

14  .  000 

77  4 

369.0 

420.0 

15 

S 

16.000 

15  250 

62.6 

298.0 

339.0 

15 

X 

16.000 

15.000 

82.  8 

394.0 

449.0 

S   =  Standard  pipe. 
X   =  Extra  stiong  pipe. 
XX    =  Double  extni  strong  pipe. 


148  APPENDICES 

102.  Resistance  of  Lead  Cable  Sheaths. 

TABLE  11. 

TABLE  FOR  DETERMINING  CURRENT  ON   LEAD   CABLE   SHEATHS  FROM 
VOLTAGE  DROP  IN  MEASURED  LENGTH  OF  SHEATH. 

Resistivity,  1  ft.  length,  1  sq.  in.  sectional  area   =  0.00010  ohm 


Outside 

Thick- 

Current 

Outside 

Thick- 

Current 

diam.  of 

ness 

Resistance 

for  1 

diam.  of 

ness 

Resistance 

for  1 

lead 

of  lead 

of  lead 

millivolt 

lead 

of  lead 

of  lead 

millivolt 

sheath 

sheath 

sheath 

per  ft. 

sheath 

sheath 

sheath 

per  ft. 

(in.) 

(64th  in.) 

^ohm  per  ft.) 

(amp.) 

(in.) 

(64th  in.) 

(ohm  per  ft.) 

(amp.) 

0.50 

4 

0.001163 

0.860 

2.00 

6 

0.0001781 

5.61 

0.50 

5 

0  .  000965 

1.036 

2.00 

7 

0.0001538 

6.50 

0.50 

6 

0  .  000836 

1.196 

2.00 

8 

0.0001359 

7.36 

0.625 

4 

0  .  000906 

1.104 

2   125 

6 

0.0001672 

5.98 

0.625 

5 

0  .  000745 

1.343 

2.125 

7 

0.0001443 

6.93 

0  .  625 

6 

0.000640    . 

1.563 

2.125 

8 

0.0001273 

7.86 

0.75 

4 

0.000741 

1.350 

2.25 

6 

0.0001575 

6.35 

0.75 

5 

0  .  000606 

1.650 

2.25 

7 

0.0001359 

7.36 

0.75 

6 

0.000518 

1.931 

2.25 

8 

0.0001198 

8.35 

0.875 

4 

0.000627 

1.594 

2.375 

6 

0.0001488 

6.72 

0.875 

5 

0.000511 

1.957 

2  .  375 

7 

0.0001284 

7.79 

0.875 

6 

0.000435 

2.300 

2.375 

8 

0.0001132 

8.83 

1.00 

5 

0.0004419 

2  .  263 

2.50 

7 

0.0001217 

8.22 

1.00 

6, 

0.0003750 

2.668 

2.50 

8 

0.0001073 

9.32 

1.00 

7 

0  .  0003268 

3.061 

2.50 

9 

0  .  0000959  , 

10,43 

.    1.00 

8 

0.0002913 

3.437 

2.625 

7 

0.0001156 

8.65 

1.125 

5 

0.0003892 

2.569 

2.625 

8 

0.0001019 

9.81 

1.125 

6 

0.0003294 

3.037 

2.625 

9 

0.0000911 

10.98 

1.125 

7 

0.0002866 

3.491 

1.125 

8 

0  .  0002547 

3.926 

2.75 

7 

0.0001102 

9.08 

2.75 

8 

0.0000971 

10.30 

1.25 

5 

0  .  0003476 

2.876 

2.75 

9 

0  .  0000868 

11.53 

1.25 

6 

0  .  0002939 

3.404 

1.25 

7 

0  .  0002552 

3.918 

2.875 

7 

0.0001050 

9.51 

1.25 

8 

0.0002265 

4.415 

2.875 

8 

0.0000927 

10.79 

2.875 

9 

0  .  0000828 

12.08 

1.375 

5 

0.0003142 

3.183 

1.375 

6 

0  .  0002650 

3  .  773 

3.00 

8 

0  .  0000887 

11.28 

1.375 

7 

0  .  0002299 

4.35 

3.00 

9 

0  .  0000792 

12.62 

1  375 

8 

0.000203S 

4.91 

3  .  00 

10 

0.0000716 

13.96 

1.50 

6 

0.0002416 

4.14 

3.125 

8 

0  .  0000849 

11.77 

1.50 

7 

0  .  0002092 

4.78 

3.125 

9 

0.0000758 

13.18 

1.50 

8 

0.0001853 

5.40 

3.125 

10 

0  .  0000686 

14.58 

1   625 

6 

0.0002218 

4.51 

3.25 

8 

0.0000815 

12.27 

1.625 

7 

0.0001920 

5.21 

3.25 

9 

0.0000728 

13.74 

1.625 

8 

0.0001698 

5.89 

3.25 

10 

0.0000659 

15.19 

1   75 

6 

0.0002051 

4.88 

3.375 

8 

0  .  0000783 

12.77 

1.75 

7 

0.0001772 

5.64 

3.375 

9 

0  .  0000700 

14.29 

1.75 

8 

0.0001567 

6.38 

3.375 

10 

0  .  0000633 

15.83 

1.875 

6 

0.0001906 

5.25 

3.50 

8 

0.0000755 

13.24 

1.875 

7 

0.0001648 

6.07 

3.50 

9 

0  .  0000674 

14.84 

1.875 

8 

0.0001456 

6.87 

3.50 

10 

0  .  0000609 

16,42 

APPENDICES 
103.     Typical  Report  Sheets. 


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Size  and  kind  of  pipe:  — 

D^-TT  ~~4-. 

Location  of  nearest  trolley 

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